Haloalkanes and Haloarenes: Class 12 Chemistry Chapter 6 Hinglish mein

Chemistry Part 2 · Hinglish notes, simulations aur practice · Official NCERT chapter PDF ↗

Published 12 Oct 2026 · Updated 12 Oct 2026

110 min
1 simulation
32 practice questions
39 MCQs

Is chapter mein aap kya seekhenge

Organohalogen compounds ko halogen atoms ki ginti aur halogen wale carbon ki kism ke hisaab se classify karna, aur unhe common aur IUPAC rules se naam dena
Carbon–halogen bond ki polarity, length aur strength ko boiling point, density, solubility aur reactivity se jodna
Alcohols, alkanes, alkenes aur doosre halides se haloalkanes, aur arenes aur diazonium salts se haloarenes banane ke liye reagents chunna
SN2 aur SN1 mechanisms samjhana, predict karna ki koi halide kaunsa mechanism follow karega, aur stereochemical result predict karna
Chiral molecules aur stereocentres pehchanna, aur optical activity, enantiomers aur racemic mixtures samjhana
Dehydrohalogenation (Zaitsev rule) aur magnesium aur sodium ke saath reactions ke products predict karna
Samjhana ki haloarenes nucleophilic substitution ka virodh kyun karte hain, phir bhi ortho/para electrophilic substitution kyun dete hain
Common polyhalogen compounds ke uses aur unke health aur environmental effects batana

NCERT Chemistry Class 12, Chapter 6, pp. 159–192 par based original companion text. Yeh NCERT se juda nahi hai aur NCERT ne ise endorse nahi kiya hai.

Kitchen mein nazar ghumao to tumhe carbon–halogen bonds anokhi jagahon par milenge. Sink ke neeche wala grey PVC pipe chloroethene ka polymer hai. Tawa ki non-stick coating $C F_{2}$ units ki ek lambi chain hai. Low-calorie sweetener sucralose table sugar hi hai jismein teen $- O H$ groups ki jagah chlorine atoms aa gaye hain, aur kai split air conditioners mein ghoomne wali gas, difluoromethane, bhi ek halogen compound hai.

In sab molecules mein carbon fluorine, chlorine, bromine ya iodine se juda hai. Chemists aise organohalogen compounds ko do families mein baantte hain, us carbon ko dekhkar jis par halogen hai. Agar woh kisi alkyl group ka $s p^{3}$ carbon hai, to compound ek haloalkane hai; agar woh aromatic ring ka $s p^{2}$ carbon hai, to compound ek haloarene hai. Hybridisation ka yeh ek fark dono families ki chemistry ko bilkul alag bana deta hai.

Definition

Haloalkane (alkyl halide)

Ek compound $R - X$ jismein halogen atom X kisi alkyl group ke $s p^{3}$ -hybridised carbon se juda hota hai.

ExampleBromoethane, $C H_{3} C H_{2} B r$ .

Definition

Haloarene (aryl halide)

Ek compound $A r - X$ jismein X seedha aromatic ring ke $s p^{2}$ -hybridised carbon se juda hota hai.

ExampleChlorobenzene, $C_{6} H_{5} C l$ .

Inhe kyun padhein? Laboratory mein C–X bond ek handle ki tarah hai: ise $- O H$ , $- O R$ , $- N H_{2}$ ya $- C N$ group se badla ja sakta hai, ya do carbon chains jodne mein use kiya ja sakta hai, isliye kai syntheses ek halide se shuru hote hain. Kai halides oils aur waxes ko achhe se dissolve karte hain, aur bahut si common medicines mein halogen atom hota hai. Doosra pehlu yeh hai ki mazboot carbon–halogen bonds ki wajah se inmein se kuch compounds soil, water aur upper air mein lambe time tak tike rehte hain; is kahani par hum chapter ke end mein wapas aayenge.

6.1 Classification

Organohalogen compounds ko hum do tarah se sort kar sakte hain: molecule mein kitne halogen atoms hain, aur har halogen kis tarah ke carbon se juda hai. Reactions predict karne ke liye doosra tareeka kaam ka hai.

6.1.1 Halogen atoms ki ginti ke aadhaar par

Ek halogen atom wala molecule monohalogen compound hai; do wala dihalogen compound; teen ya zyada wala polyhalogen (tri-, tetra-, …) compound. Table mein har kism ka ek aliphatic aur ek aromatic example diya hai.

Table 6.1Halogen atoms ginna

Ginti	Chain par	Ring par
ek (mono)	$C H_{3} C H_{2} B r$	$C_{6} H_{5} I$
do (di)	$C l C H_{2} C H_{2} C l$	$C_{6} H_{4} C l_{2}$
teen (tri)	$C H I_{3}$	$C_{6} H_{3} B r_{3}$
kai (poly)	$C C l_{4}$	$C_{6} C l_{6}$

6.1.2 sp³ C—X bond wale compounds

Alkyl halides, R–X. Yahan halogen alkyl chain ke ek saturated ( $s p^{3}$ ) carbon par hota hai. Aisa halide primary (1°), secondary (2°) ya tertiary (3°) hai, yeh tay karne ke liye X wale carbon se jude carbon atoms gino: ek, do ya teen (Fig. 6.1). Halomethanes, $C H_{3} X$ , ka koi carbon neighbour hota hi nahi, isliye unhe alag class maana jaata hai. Open-chain monohaloalkanes general formula $C_{n} H_{2 n + 1} X$ mein fit hote hain.

Allylic aur benzylic halides. Do tarah ke neighbours ko khaas naam milte hain. Agar X wala $s p^{3}$ carbon kisi C=C double bond ke ek carbon se juda ho, to halide allylic hai, jaise 3-chloroprop-1-ene, $C H_{2} = C H - C H_{2} C l$ . Agar woh aromatic ring se juda ho, to halide benzylic hai, jaise $C_{6} H_{5} C H_{2} C l$ . Dono khud bhi 1°, 2° ya 3° ho sakte hain: $C_{6} H_{5} C (C H_{3})_{2} B r$ ek tertiary benzylic bromide hai. Bagal wala π system in halides ko kaafi zyada reactive bana deta hai (SN1 mechanism).

1/4Ghere hue carbon se jude carbons gino: ek, do ya teen.

Fig. 6.1X wale carbon ko dekho: uska hybridisation aur uske neighbours class tay karte hain.NCERT 6.1.2 · p. 160

Upar paanch category chips hain: heading 'X sp3 carbon par' ke neeche alkyl, allylic aur benzylic, aur heading 'X sp2 carbon par' ke neeche vinylic aur aryl. Step 1 alkyl ko highlight karta hai aur chloroethane, 2-bromopropane aur 2-iodo-2-methylpropane dikhata hai; halogen wala carbon ghera hua hai aur us par jude carbons ki ginti ke hisaab se 1°, 2° aur 3° likha hai. Step 2 allylic aur benzylic ko highlight karta hai aur 3-bromopropene aur benzyl chloride dikhata hai, jismein CH2 ghera hua hai. Step 3 vinylic ko highlight karta hai aur chloroethene aur ek cyclohexene dikhata hai jismein bromine double-bond carbon par hai. Step 4 aryl ko highlight karta hai aur chlorobenzene aur 4-bromotoluene dikhata hai, jismein halogen wala ring carbon ghera hua hai.

6.1.3 sp² C—X bond wale compounds

Agar X wala carbon $s p^{2}$ -hybridised ho, to halogen ka bartaav bilkul alag hota hai. Vinylic halide mein X ek C=C double bond ke do carbons mein se ek par hota hai, jaise chloroethene, $C H_{2} = C H C l$ (vinyl chloride, PVC ka monomer). Aryl halide mein X seedha aromatic ring ke carbon se juda hota hai, jaise bromobenzene mein. Vinylic aur aryl halides dono ka C–X bond ziddi hota hai; iski wajah hum Section 6.7.2 mein dekhenge.

Quick check

3 mein se 1

2-bromo-2-methylbutane,

(C H_{3})_{2} C (B r) C H_{2} C H_{3}

, ko tum kaise classify karoge?

primary alkyl halidesecondary alkyl halidetertiary alkyl halidevinylic halide

Answer dekho

Answer (C) tertiary alkyl halide

Br wala carbon teen doosre carbons (do

C H_{3}

aur ek

C H_{2}

) se juda hai, isliye bromide tertiary hai. Yeh vinylic nahi hai: koi double bond hai hi nahi.

6.2 Nomenclature

Har halide ke do tarah ke naam ho sakte hain. Purana common name kisi salt ke naam jaisa lagta hai: pehle alkyl group, phir halide, do words mein (isopropyl chloride, allyl bromide). IUPAC name mein halogen parent hydrocarbon ke aage prefix ban jaata hai (fluoro, chloro, bromo, iodo): 2-chloropropane, 3-bromoprop-1-ene.

Usual IUPAC rules hi lagte hain. Sabse lambi chain chuno (jismein koi C=C ya C≡C ho to woh bhi shaamil ho), use aise number karo ki locants sabse chhote aayein, aur prefixes alphabetical order mein likho. Alkane mein halogen aur alkyl branch ka darja barabar hota hai, isliye agar dono ends se numbering same locant set de, to jo prefix alphabet mein pehle aata hai use chhota number milta hai. Alkene ya alkyne mein chhote locant ke liye multiple bond ko priority milti hai.

Rings aur dihalides do aur conventions jodte hain (Fig. 6.2). Benzene ring par ek halogen ho to dono systems same naam dete hain (iodobenzene). Ring par do groups hon to common name batata hai ki doosra group pehle ke relative kahan hai: o- (ortho, bilkul bagal mein), m- (meta, beech mein ek ring carbon) ya p- (para, aamne-saamne). IUPAC iski jagah ring ko number karta hai: 1,2-, 1,3- ya 1,4-. Chain par, ek hi carbon par do same halogens geminal (gem) dihalide banate hain, jise common system mein alkylidene halide kehte hain; bagal-bagal ke carbons par do halogens vicinal (vic) dihalide banate hain, yaani alkylene dihalide. IUPAC ko khaas words ki zaroorat nahi: dono sahi locants wale dihaloalkanes hain.

Fig. 6.2Common names o-, m-, p- aur gem/vic use karte hain; IUPAC names numbers use karte hain.

Left mein teen benzene rings hain, har ek par do chlorine atoms: bagal wale ring carbons par (label ortho, o-, aur 1,2-), beech mein ek ring carbon chhodkar (meta, m-, 1,3-) aur aamne-saamne ke carbons par (para, p-, 1,4-). Right mein, ek line ke paar, do condensed formulas: CH3–CHBr2 jismein CHBr2 group box mein hai, label gem: ek carbon, 1,1-dibromoethane; aur BrCH2–CH2Br jismein dono carbons box mein hain, label vic: bagal ke Cs, 1,2-dibromoethane.

Table 6.2Kuch halides ke common aur IUPAC names

Structure	Common; IUPAC
$C H_{3} C H_{2} C H_{2} I$	n-propyl iodide; 1-iodopropane
$(C H_{3})_{2} C H C l$	isopropyl chloride; 2-chloropropane
$(C H_{3})_{2} C H C H_{2} B r$	isobutyl bromide; 1-bromo-2-methylpropane
$(C H_{3})_{3} C I$	tert-butyl iodide; 2-iodo-2-methylpropane
$C_{6} H_{11} B r$ (ek ring)	cyclohexyl bromide; bromocyclohexane
$C H_{2} = C H C H_{2} I$	allyl iodide; 3-iodoprop-1-ene
$C F_{2} = C F_{2}$	tetrafluoroethylene; tetrafluoroethene
$C_{6} H_{5} C H_{2} B r$	benzyl bromide; (bromomethyl)benzene
$C H_{3} C H B r_{2}$	ethylidene bromide; 1,1-dibromoethane
$B r C H_{2} C H_{2} B r$	ethylene dibromide; 1,2-dibromoethane
$m$ - $B r C_{6} H_{4} C H_{3}$	m-bromotoluene; 1-bromo-3-methylbenzene

Example 6.1NCERT Example 6.1 · p. 162

C₄H₇Br ke ring isomers

Ek compound $C_{4} H_{7} B r$ mein ya to ek ring hai ya ek C=C double bond. Har woh structural isomer dhoondho jismein ring ho aur double bond na ho, har ek ka naam do, aur batao ki woh primary, secondary ya tertiary bromide hai.

Pehle khud try karo. Phir solution ek-ek step karke kholo.

Example 6.2NCERT Example 6.2 · p. 163

Unsaturated halides ke naam

Har compound ka IUPAC name do aur batao ki halogen allylic hai, vinylic hai ya kisi saadharan alkyl carbon par hai.

$C H_{2} = C H C H_{2} C H (C l) C H_{3}$
$C H_{3} C H = C (C l) C H_{3}$
$(C H_{3})_{2} C = C H C H_{2} I$
$C H_{2} = C H C H (I) C H_{2} C H_{3}$

Pehle khud try karo. Phir solution ek-ek step karke kholo.

Practice · 1 question

Practice: halides ke naam: answers ke saath

1
Short answerEasyNCERT Intext Question 6.1
Har compound ka condensed structural formula likho.
1. 2-Bromo-4-methylhexane
  Solution dikhao
  $C H_{3} C H (B r) C H_{2}$ – $C H (C H_{3}) C H_{2} C H_{3}$
2. 1-Iodo-2,2-dimethylbutane
  Solution dikhao
  $I C H_{2} C (C H_{3})_{2}$ – $C H_{2} C H_{3}$
3. 4-Bromo-3-ethylhept-1-ene
  Solution dikhao
  $C H_{2} = C H$ – $C H (C_{2} H_{5})$ – $C H (B r) C H_{2}$ – $C H_{2} C H_{3}$
4. 1,3-Dichlorobut-1-ene
  Solution dikhao
  $C l C H = C H$ – $C H (C l) C H_{3}$ : ek vinylic aur ek allylic chlorine.
5. 2-Bromo-1-chloro-4-methylbenzene
  Solution dikhao
  Ek benzene ring jismein Cl C1 par, Br agle carbon (C2) par aur $C H_{3}$ C4 par hai, yaani Cl ke para.

Quick check

3 mein se 1

(C H_{3})_{2} C H C H_{2} C H_{2} B r

ka IUPAC name kya hai?

4-bromo-2-methylbutane1-bromo-3-methylbutane2-methyl-4-bromobutane1-bromo-2-methylbutane

Answer dekho

Answer (B) 1-bromo-3-methylbutane

Jis end ke paas substituent zyada nazdeek ho, wahan se number karo: Br C1 par aur methyl C3 par, yaani {1, 3}, jo {2, 4} se chhota hai. Prefixes alphabetical order mein aate hain, isliye 1-bromo-3-methylbutane. Option D methyl ko galat carbon par rakh deta hai.

6.3 C—X bond ka nature

Neeche wali table ki electronegativity row se shuru karo: har halogen carbon (2.5) se zyada zor se electrons kheenchta hai. Isliye C–X bond ka bonding pair halogen ke zyada paas rehta hai, jis par partial negative charge (δ−) aa jaata hai, aur carbon partially positive (δ+) reh jaata hai. Is chapter ki lagbhag har reaction mein electron-rich reagents isi δ+ carbon ko target karte hain; neeche wala simulation tumhe yeh kheenchaav mehsoos karne deta hai.

Ab bond-length row padho. F se I tak har step halogen mein electrons ka ek shell jodta hai, aur bond 138 pm se 213 pm tak lamba ho jaata hai. Bond jitna lamba, bonding orbitals ka overlap utna kamzor, isliye bond enthalpy lagbhag aadhi gir jaati hai, 460 se 239 kJ mol⁻¹ tak. Chaaron mein C–I bond todna sabse aasaan hai.

Table 6.3Halomethanes CH₃X mein carbon–halogen bonds (gas-phase values, rounded; EN = X ki electronegativity, μ = dipole moment)NCERT Table 6.2 · p. 164

Property	F	Cl	Br	I
EN	4.0	3.2	3.0	2.7
length / pm	138	178	193	213
enthalpy / kJ mol⁻¹	460	350	294	239
μ / D	1.86	1.89	1.82	1.62

Dipole moments ek surprise dete hain: sabse bada dipole moment fluoromethane ka nahi, chloromethane ka hai. Dipole moment charge separation guna distance hota hai. Fluorine sabse zor se kheenchta hai, lekin C–F bond itna chhota hai ki product lambe C–Cl bond se thoda kam reh jaata hai. Jab kai C–X bonds hon, to unke bond dipoles vectors ki tarah judte hain; tetrachloromethane mein chaaron tetrahedron ke corners ki taraf point karte hain aur poori tarah cancel ho jaate hain, isliye $C C l_{4}$ ka dipole moment bilkul zero hai.

SimulationPolar C–X bond do partial charges ke roop mein

Stage ke beech mein do fixed point charges bagal-bagal hain: left mein ek positive charge jo carbon atom hai aur right mein ek negative charge jo halogen hai. Field lines positive se negative charge ki taraf jaati hain. Ek chhota negative test charge, jo electron-rich nucleophile hai, kahin bhi drag kiya ja sakta hai; ek arrow aur readout us par lagne wale force ka size aur direction dikhate hain.

Fig. 6.3+ charge δ+ carbon hai aur − charge δ− halogen. Chhota negative test charge paas aate nucleophile ka role nibhata hai.

Try karo

Negative test charge ko pair ke chaaron taraf dheere-dheere drag karo. Use sabse zyada zor se kahan kheencha jaata hai, aur kis atom ki taraf?
Test charge ko halogen wale end ke thoda aage, dono charges se guzarti line par rakho. Kya woh attract hota hai ya door dhakela jaata hai?
Test charge ko carbon ke peeche le jao, halogen se ulti taraf. Dhyaan do ki SN2 reaction mein nucleophile isi raaste se aata hai.

Quick check

3 mein se 1

C–X bonds ko sabse strong se sabse weak tak arrange karo.

C–Br
C–Cl
C–I
C–F

Answer dekho

Answer

C–F
C–Cl
C–Br
C–I

Halogen jaise-jaise bada aur bond lamba hota hai, bond enthalpy girti hai: lagbhag 460, 350, 294 aur 239 kJ per mole.

6.4 Haloalkanes banane ke tareeke

Shuru karne ke teen achhe raaste hain. Alcohols saste hain aur aasaani se milte hain; hydrocarbons, jo substitution ya addition se halogens le sakte hain; aur doosre halides, jinka halogen kisi aur halogen se badla ja sakta hai.

6.4.1 Alcohols se

Kaam hai $- O H$ group ko halogen se replace karna. Hydroxide ek kharab leaving group hai, isliye neeche ka har reagent pehle OH ko kisi aisi cheez mein badalta hai jo aasaani se nikal jaaye. Acids use protonate karke $- O H_{2}^{+}$ banate hain, jo water ke roop mein nikal jaata hai, jabki phosphorus aur sulfur halides use phosphite ya chlorosulfite ester mein badal dete hain jismein ek excellent leaving group hota hai.

Table 6.4Reagents jo R–OH ko R–X mein badalte hainNCERT 6.4.1 · p. 164

Reagent	By-products	Notes
conc. $H C l$ + anhydrous $Z n C l_{2}$	$H_{2} O$	1° aur 2° alcohols ko $Z n C l_{2}$ catalyst chahiye; 3° alcohol room temperature par hilane se sirf conc. HCl ke saath react kar leta hai
$H B r$ (48 % aqueous), ya $N a B r$ + conc. $H_{2} S O_{4}$	$H_{2} O$ ( $N a H S O_{4}$ )	bromides; reflux mein garam karo
$K I$ ya $N a I$ + 95 % $H_{3} P O_{4}$	$H_{2} O$	iodides; phosphoric acid isliye use hota hai kyunki $H_{2} S O_{4}$ HI ko oxidise karke $I_{2}$ bana deta
$P C l_{3}$ (3 mol ROH ke liye 1 mol)	$H_{3} P O_{3}$	chlorides
$P C l_{5}$	$P O C l_{3}$ + $H C l$	chlorides
red P + $B r_{2}$ ya $I_{2}$	$H_{3} P O_{3}$	$P B r_{3}$ ya $P I_{3}$ flask mein hi (in situ) banta hai
$S O C l_{2}$ (thionyl chloride)	$S O_{2}$ (g) + $H C l$ (g)	chlorides; dono by-products gas banke nikal jaate hain, isliye product ko kam purify karna padta hai

Thionyl chloride wala raasta

\begin{aligned} R - O H + S O C l_{2} \\ \overset{}{\to} R - C l + S O_{2} ↑ \\ + H C l ↑ \end{aligned}

Hydrogen halides ke saath tertiary alcohols sabse tez aur primary sabse dheere react karte hain (3° > 2° > 1°), kyunki zyada substituted carbon protonated $- O H_{2}^{+}$ group ko zyada aasaani se chhod deta hai. Practice mein chloride banane ke liye ya to dry HCl gas ki stream alcohol mein guzaarte hain ya alcohol ko concentrated hydrochloric acid ke saath reflux karte hain. Is poore section ke exception phenols hain: ring ke saath overlap unke C–O bond ko itna mazboot kar deta hai ki woh tootta hi nahi, aur aryl halides ke liye Section 6.5 wale raaste chahiye.

6.4.2 Hydrocarbons se

(I) Alkanes se, free-radical halogenation dwara. Ultraviolet light (ya heat) $C l_{2}$ ya $B r_{2}$ ko atoms mein tod deti hai, jo ek chain reaction mein alkane se ek-ek karke hydrogen atoms kheench lete hain. Dikkat yeh hai ki choice nahi milti. Chlorine atom lagbhag har C–H bond par attack kar deta hai, aur jo monochloride banta hai us par phir se attack ho sakta hai, isliye flask mein kai isomers aur di- aur trichlorides ka mixture ban jaata hai jinke boiling points bahut paas-paas hote hain. Isiliye chemists ek pure haloalkane banane ke liye yeh raasta kam hi use karte hain. (Bromine atoms zyada choosy hote hain aur tertiary hydrogens pasand karte hain, lekin bromination bhi kuch mixture deta hai.)

4/4c replace karne par tertiary chloride banta hai; d replace karne par ek aur primary chloride banta hai.

Fig. 6.4Molecule ki symmetry se jude hydrogens same product dete hain, isliye hum hydrogen atoms nahi, hydrogen ki kism ginte hain.

3-methylpentane ka condensed structure dikhaya gaya hai: CH3–CH2–CH–CH2–CH3, jiske beech wale CH se ek CH3 branch latki hai. Step 1 sirf molecule dikhata hai. Step 2 groups par tag lagata hai: dono end CH3 groups a hain, dono CH2 groups b, beech ka CH c aur branch CH3 d, saath mein note ki same letter ka matlab same tarah ka hydrogen hai, isliye chaar monochlorides ban sakte hain. Step 3 a aur b replace karne se bane products list karta hai: 1-chloro-3-methylpentane aur 2-chloro-3-methylpentane. Step 4 c aur d se bane products jodta hai: 3-chloro-3-methylpentane aur 3-(chloromethyl)pentane.

Example 6.3NCERT Example 6.3 · p. 165

Monochlorination products ginna

3-methylpentane, $C H_{3} C H_{2} C H (C H_{3}) C H_{2} C H_{3}$ , ka free-radical chlorination kitne structurally alag monochlorides $C_{6} H_{13} C l$ de sakta hai? Unke naam batao.

Pehle khud try karo. Phir solution ek-ek step karke kholo.

(II) Alkenes se. (i) Hydrogen halide jodna. HCl, HBr ya HI C=C bond ke across judkar alkyl halide dete hain. Unsymmetrical alkene ke saath do products ban sakte hain, aur major product Markovnikov's rule (Class 11) follow karta hai. Hydrogen us double-bond carbon par jaata hai jis par pehle se zyada hydrogens hain, kyunki woh raasta zyada stable carbocation se hokar jaata hai. Peroxide ki maujoodgi mein HBr (sirf HBr) ulti taraf judta hai.

Markovnikov addition

\begin{aligned} R C H = C H_{2} + H B r \\ \overset{}{\to} R C H (B r) C H_{3} \end{aligned}

(ii) Halogen jodna. Alkene ko red-brown bromine solution ki kuch boondon ke saath hilao, aur colour kuch hi seconds mein gaayab ho jaata hai: har $B r_{2}$ molecule ek C=C bond ke across jud gaya, aur colourless vic-dibromide ban gaya. Alkanes aise react nahi karte, isliye gaayab hota colour unsaturation ka ek quick laboratory test hai.

1,2-dibromoethane

\begin{aligned} C H_{2} = C H_{2} + B r_{2} \\ \overset{}{\to} B r C H_{2} C H_{2} B r \end{aligned}

Try karke dekho

Kaunse cooking oils mein C=C bonds hain?

Tumhe chahiye

liquid paraffin
sunflower oil
coconut oil
dilute bromine water (teacher handle karenge)
stoppers wali teen test tubes

Pehle guess karo

Tumhare hisaab se kaunsa liquid bromine water ka colour sabse poori tarah hata dega?

liquid paraffinsunflower oilcoconut oil

Har liquid ka 2 mL alag-alag, label lagi test tubes mein daalo.
Tumhare teacher har tube mein 1 mL dilute bromine water daalenge.
Stopper lagao, 30 seconds tak hilao aur layers ko baithne do.
Har tube ka colour sirf bromine water wali ek tube se compare karo.

Table 6.5Observations

Liquid	Hilane ke baad colour
Liquid paraffin
Sunflower oil
Coconut oil

Tumhari entries apne aap save hoti hain.

6.4.3 Halogen Exchange

Alkyl chloride ya bromide ko iodide mein badalne ke liye use dry acetone mein sodium iodide ke saath garam karo: yeh hai Finkelstein reaction. Halogens ka exchange reversible hai, lekin acetone palda jhuka deta hai. Sodium iodide usmein achhe se dissolve hota hai, jabki sodium chloride aur sodium bromide mushkil se dissolve hote hain aur white solid ban kar neeche baith jaate hain. Is tarah solution se nikalne wala har ion pair equilibrium se hat jaata hai, isliye, jaisa Le Chatelier's principle predict karta hai, reaction alkyl iodide ki taraf chalta rehta hai.

Finkelstein reaction

\begin{aligned} R C l + N a I \overset{a c e t o n e}{\to} \\ R I + N a C l ↓ \end{aligned}

Alkyl fluorides Swarts reaction se bante hain: alkyl chloride ya bromide ko kisi inorganic fluoride ke saath garam kiya jaata hai, jaise antimony(III) fluoride, $S b F_{3}$ , cobalt(II) fluoride, $C o F_{2}$ , silver fluoride, $A g F$ , ya mercury(I) fluoride, $H g_{2} F_{2}$ . Fluorine gas khud is kaam ke liye bekaar hai, kyunki woh organic compounds par explosively attack karti hai.

Swarts reaction

\begin{aligned} C_{2} H_{5} B r + A g F \\ \overset{}{\to} C_{2} H_{5} F + A g B r \end{aligned}

6.5 Haloarenes banana

(i) Halogen seedha ring par. Akele chlorine aur bromine itne weak electrophile hain ki benzene par attack nahi kar paate. Lewis acid catalyst, yaani iron filings ya iron(III) chloride ya bromide, halogen molecule ko polarise karta hai, aur uska positive end ring ke ek hydrogen ko replace kar deta hai. Jab arene par methyl group jaisi side chain ho, to reaction andhere mein kiya jaata hai, kyunki light side chain par radical reaction shuru kar degi. Toluene 2- aur 4-halotoluene ka mixture deta hai; para isomer ka melting point kaafi zyada hai aur woh crystallise hokar nikal jaata hai, isliye dono ko alag karna aasaan hai.

Ring chlorination (andhere mein)

\begin{aligned} C_{6} H_{6} + C l_{2} \\ \overset{F e C l_{3}}{\to} C_{6} H_{5} C l \\ + H C l \end{aligned}

Baaki do halogens gadbad karte hain. Iodination reversible hai, kyunki isse bana HI iodobenzene ko reduce karke wapas benzene bana deta hai; isliye $H N O_{3}$ ya $H I O_{4}$ jaisa oxidising agent daala jaata hai jo HI ko bante hi khatam kar de. Fluorine ki problem ulti hai: woh arenes ke saath itni violently react karti hai ki ring fluorination control nahi ho sakta.

(ii) Aromatic amine se: Sandmeyer reaction. Yeh raasta hydrogen ki jagah $- N H_{2}$ group ko replace karta hai, isliye halogen theek wahin aata hai jahan amino group tha. Pehle amine ko diazotise kiya jaata hai: use thande hydrochloric acid mein lekar 273–278 K par rakha jaata hai aur sodium nitrite daala jaata hai, jisse arenediazonium salt, $A r N_{2}^{+} X^{-}$ , banta hai. Yeh salts garam hone par decompose ho jaate hain, isliye solution seedha agle step mein jaata hai. Phir copper(I) chloride ya copper(I) bromide $- N_{2}^{+}$ group ko Cl ya Br se badal deta hai, aur nitrogen gas bubbles banke nikalti hai. Iodides banana aur bhi aasaan hai: sirf potassium iodide kaafi hai, copper salt ki zaroorat hi nahi (Fig. 6.5).

Sandmeyer raasta (thanda diazotisation, phir CuCl)

\begin{aligned} A r N H_{2} \\ \overset{N a N O_{2}, H C l}{\to} A r N_{2}^{+} \\ \overset{C u C l}{\to} A r C l + N_{2} ↑ \end{aligned}

Fig. 6.5Ring halogenation H ki jagah X lagata hai; Sandmeyer raasta X ko wahan rakhta hai jahan amino group tha.

Arrows se jude boxes ki do rows. Upar wali row, arene se: benzene, C6H6, Cl2, FeCl3, dark label wale arrow se chlorobenzene, C6H5Cl, tak jaata hai. Neeche wali row, amine se: 4-methylaniline, CH3C6H4NH2, NaNO2 aur HCl, cold, 273 se 278 K label wale arrow se diazonium salt CH3C6H4N2+ Cl− tak jaata hai, jo garam rang ke box mein bana hai yeh dikhane ke liye ki use turant use karna hai. Diazonium salt se CuCl label wala ek arrow upar 4-chlorotoluene, CH3C6H4Cl, tak jaata hai, aur KI label wala doosra arrow neeche 4-iodotoluene, CH3C6H4I, tak.

Example 6.4NCERT Example 6.4 · p. 167

Addition products predict karna

Har case mein major organic product likho.

$(C H_{3})_{2} C = C H_{2} + H B r$
$C H_{3} C H_{2} C H_{2} C H = C H_{2} + H B r$ , peroxide ki maujoodgi mein
$C_{6} H_{5} C H = C H C H_{3} + H B r$
cyclopentene + $B r_{2}$

Pehle khud try karo. Phir solution ek-ek step karke kholo.

6.6 Physical Properties

Taaze distil kiye haloalkanes colourless hote hain. Lekin dhoop wali shelf par rakhi iodoalkane ki bottle dheere-dheere brown ho jaati hai: light kuch C–I bonds tod deti hai, aur nikla hua iodine liquid ko rang deta hai (bromides bhi aisa karte hain, par dheere). Sirf sabse halke members, jaise chloromethane (b.p. 249 K) aur refrigerant chlorodifluoromethane, room temperature par gases hain; bromoethane (b.p. 311 K) se upar sab liquids hain, aur kai polyhalides solids hain. Chloroform jaise kam boiling point wale halides ki smell halki meethi hoti hai.

Boiling points. Halide apne parent alkane se kaafi zyada temperature par ubalta hai: butane 273 K par ubalta hai, 1-chlorobutane 352 K par. Jab hydrogen ki jagah halogen aata hai to do tarah ke attractions badhte hain. Polar C–X bond dipole–dipole attraction jodta hai, aur halogen ka bada, aasaani se distort hone wala electron cloud dispersion (van der Waals) forces ko mazboot karta hai. (Halide ko barabar molar mass wale alkane se compare karna gumraah kar sakta hai. Bromine mass to bahut jodta hai par surface kam, isliye bromoethane, M = 109, 311 K par ubalta hai jabki heptane, M = 100, 371 K par.)

Ek hi alkyl group ke liye boiling point is order mein badhta hai: R–F < R–Cl < R–Br < R–I. Bond dipole to Cl se I tak girta hai, phir bhi boiling point chadhta hai, kyunki bade halogen atoms mein kaafi zyada electrons hote hain aur dispersion forces jeet jaati hain. Isomers mein branching boiling point ghatati hai: branched molecule zyada compact, lagbhag spherical hota hai aur apne neighbours ko kam area par chhoota hai. Fig. 6.6 dono trends dikhata hai.

2/3Har bada halogen butyl halide ka boiling point badhata hai.

Fig. 6.6Bhaari halogens boiling point badhate hain; branching use ghatati hai.NCERT Fig. 6.1 · p. 168

Ek chart jiske vertical axis par kelvin mein boiling point lagbhag 250 se 420 tak hai. Step 1 sirf parent alkane butane ko 273 K par ek square ke roop mein dikhata hai. Step 2 1-fluoro-, 1-chloro-, 1-bromo- aur 1-iodobutane ke chaar jude points 306, 352, 375 aur 404 K par jodta hai, jo lagaatar badhte hain. Step 3 unki jagah chaar isomeric butyl chlorides se guzarti dashed line dikhata hai: n-butyl 352 K, sec-butyl 341 K, isobutyl 342 K aur tert-butyl 324 K; sabse zyada branched sabse neeche hai.

Melting points aur symmetry. Teenon dichlorobenzenes ke boiling points kuch hi kelvin ke andar hain (1,2-, 1,3- aur 1,4-isomers ke liye 453, 446 aur 447 K), lekin unke melting points bahut alag hain: 256 K, 248 K aur 327 K. Melting is par depend karti hai ki molecules crystal mein kitne achhe se pack hote hain, aur symmetrical para isomer kaafi saafi se stack hota hai. Isiliye 1,4-dichlorobenzene solid hai (kabhi yeh moth crystals ke naam se bikta tha) jabki baaki do liquids hain.

Solubility. Haloalkane polar hai, phir bhi water mein mushkil se milta hai: dichloromethane bhi sirf lagbhag 1.3 g per 100 g tak dissolve hota hai. Energy ka hisaab socho. Liquid water hydrogen bonds ka ek kasa hua network hai, aur haloalkane molecule usmein tabhi ghus sakta hai jab kuch hydrogen bonds toot jaayein. Badle mein woh water ko jo dipole aur dispersion attractions deta hai woh kaafi weak hain, isliye yeh lena-dena faayde ka nahi. Kisi doosre organic liquid ke saath milane par haloalkane lagbhag barabar size ke attractions khota aur paata hai, aur dono poori tarah mix ho jaate hain.

Density. Halogen atom us hydrogen se kaafi bhaari hai jiski jagah woh aata hai, isliye density halogen atoms ke mass aur ginti ke saath badhti hai. Bada alkyl part is effect ko kam kar deta hai, isliye ek series mein chain lambi hone par density ghatti hai. Bromides, iodides aur zyaadatar polychloro compounds water se zyada dense hain aur uske neeche doob jaate hain.

Table 6.6Lagbhag 293 K par kuch halogen compounds ki densities (g mL⁻¹)NCERT Table 6.3 · p. 169

Trend	Compound	Density
bhaari halogen	1-chlorobutane	0.89
bhaari halogen	1-bromobutane	1.28
bhaari halogen	1-iodobutane	1.62
lambi chain	iodomethane	2.28
lambi chain	iodoethane	1.95
zyada halogen	1,2-dichloroethane	1.25
zyada halogen	1,1,2-trichloroethane	1.44
zyada halogen	1,1,2,2-tetrachloroethane	1.59

Quick check

4 mein se 1

Boiling point ke badhte order mein arrange karo (sabse kam pehle).

$C H_{3} I$
$C H_{3} F$
$C H_{3} B r$
$C H_{3} C l$

Answer dekho

Answer

$C H_{3} F$
$C H_{3} C l$
$C H_{3} B r$
$C H_{3} I$

Methyl group same, halogen bada: F se I tak dispersion forces badhti hain. Boiling points lagbhag 195, 249, 277 aur 316 K hain.

6.7 Chemical Reactions

Haloalkanes teen main tarah se react karte hain. Ek nucleophile halogen ki jagah le sakta hai (nucleophilic substitution); ek base HX kheench kar double bond chhod sakta hai (elimination); aur ek metal carbon aur halogen ke beech ghus sakta hai (reaction with metals). Haloarenes alag rules follow karte hain, jinhe hum Section 6.7.2 mein dekhenge.

6.7.1 Haloalkanes ki reactions

Nucleophilic substitution

Nucleophile (Nu) ek electron-rich species hai: $O H^{-}$ ya $C N^{-}$ jaisa anion, ya lone pair wala neutral molecule jaise $N H_{3}$ ya $H_{2} O$ . Haloalkane ke δ+ carbon ki taraf kheencha hua yeh ek electron pair donate karta hai aur wahan naya bond banata hai. Usi samay C–X bond tootta hai aur halogen dono bonding electrons lekar halide ion ke roop mein nikal jaata hai; yahi leaving group hai. Ek group ki jagah doosra group aane ko nucleophilic substitution kehte hain, aur isse ek hi haloalkane ko alcohols, ethers, amines, nitriles aur bahut kuch mein badla ja sakta hai.

Nucleophilic substitution

\begin{aligned} N u^{-} + R - X \\ \overset{}{\to} R - N u + X^{-} \end{aligned}

Definition

Nucleophile

Ek electron-pair donor jo electron-poor carbon atom par attack karta hai aur usse naya bond banata hai.

Example $O H^{-}$ , $C N^{-}$ , $I^{-}$ , $N H_{3}$ , $H_{2} O$ .

Nucleophile chuno, aur tumne product chun liya. Table kuch common reagents ko us atom ke hisaab se sort karti hai jo carbon se naya bond banata hai, aur har baar haloalkane bromoethane hi hai.

Table 6.7Bromoethane, CH₃CH₂Br, kya banta hai, attack karne wale atom ke hisaab seNCERT Table 6.4 · p. 170

Reagent (atom)	Product (family)
$N a O H$ ya $K O H$ , aq (O)	$C H_{3} C H_{2} O H$ , ethanol (alcohol)
$C H_{3} O N a$ (O)	$C H_{3} C H_{2} O C H_{3}$ , methoxyethane (ether)
$C H_{3} C O O A g$ (O)	$C H_{3} C O O C H_{2} C H_{3}$ , ethyl ethanoate (ester)
$K N O_{2}$ (O)	$C H_{3} C H_{2} - O - N = O$ , ethyl nitrite (alkyl nitrite)
$N H_{3}$ , excess (N)	$C H_{3} C H_{2} N H_{2}$ , ethanamine (1° amine)
$C H_{3} N H_{2}$ (N)	$C H_{3} C H_{2} N H C H_{3}$ , N-methylethanamine (2° amine)
$A g N O_{2}$ (N)	$C H_{3} C H_{2} N O_{2}$ , nitroethane (nitroalkane)
$A g C N$ (N)	$C H_{3} C H_{2} N C$ , ethyl isocyanide (isocyanide)
$K C N$ (C)	$C H_{3} C H_{2} C N$ , propanenitrile (nitrile)
$H C \equiv C N a$ (C)	$C H_{3} C H_{2} C \equiv C H$ , but-1-yne (alkyne)
acetone mein $N a I$ (I)	$C H_{3} C H_{2} I$ , iodoethane (alkyl iodide)
$L i A l H_{4}$ (H)	$C H_{3} C H_{3}$ , ethane (alkane)

Cyanide aur nitrite wali rows phir se dekho: har ion do baar aata hai, har baar alag atom se attack karta hua. Cyanide ke carbon aur nitrogen dono par lone pairs hain; nitrite oxygen se ya nitrogen se bond bana sakta hai. Aise do attacking sites wali species ko ambident nucleophiles kehte hain. Kaunsa site use hoga, yeh salt par depend karta hai. Potassium cyanide ke saath ion solution mein free hota hai aur carbon se bond banata hai, jisse nitrile banta hai. Silver cyanide mein carbon wala end pehle se ek kaafi had tak covalent Ag–C bond mein bandha hota hai, isliye sirf nitrogen ka lone pair available hota hai aur isocyanide banta hai. Nitrite bhi isi tarah behave karta hai, jaisa agla example dikhata hai.

Definition

Ambident nucleophile

Aisa nucleophile jismein do alag atoms hon jo dono electron pair donate kar sakte hain, isliye woh do alag products de sakta hai.

Example $C N^{-}$ (C ya N), $N O_{2}^{-}$ (O ya N).

Example 6.5NCERT Example 6.5 · p. 171

Ek salt, do products

Bromoethane potassium nitrite ke saath mainly ethyl nitrite deta hai, lekin silver nitrite ke saath mainly nitroethane. Samjhao.

Pehle khud try karo. Phir solution ek-ek step karke kholo.

SN2 mechanism

Nucleophilic substitution do alag raaston se hota hai. Inhe alag pehchanne ke liye chemists dekhte hain ki rate concentrations par kaise depend karta hai. Acetone jaise solvent mein thode water ke saath bromoethane aur hydroxide ion ke liye, $[C H_{3} C H_{2} B r]$ double karne par rate double hota hai, aur $[O H^{-}]$ double karne par bhi. Rate dono ke proportional hai, isliye reaction overall second order hai.

SN2 rate law

rate = k [R - X] [N u^{-}]

(6.1)

Rate law mein dono reactants aate hain kyunki dono ek hi, akele step mein maujood hain. Socho ki nucleophile halogen ke bilkul opposite side se aata hai, jahan woh halogen ke electron cloud se bacha rehta hai. Bond banna aur bond tootna alag-alag events nahi, ek hi smooth change hain. Aadhe raaste par, transition state par, carbon partial bonds se Nu aur X dono se juda hota hai, jo uske through ek seedhi line mein hote hain. Uske baaki teen groups unke beech ke plane mein flat dab jaate hain: ek carbon ke around paanch groups. Aisi arrangement sirf ek pal ke liye hoti hai aur kabhi isolate nahi ki ja sakti. Jaise-jaise X door jaata hai, teen groups chalte rehte hain aur aakhir mein doosri taraf point karne lagte hain, yaani carbon ke around ki arrangement andar-bahar palat jaati hai (Fig. 6.7).

2/3Carbon ke around paanch groups: I aur Cl partly bonded, teen groups ek plane mein.

Fig. 6.7Back-side attack carbon ke baaki teen bonds ko andar-bahar palat deta hai.NCERT Fig. 6.2 · p. 171

Ek carbon atom par wedge par hydrogen, plane mein methyl group aur dash par ethyl group hai, sab left ki taraf jhuke hue, aur right mein chlorine juda hai. Step 1 bilkul left mein ek iodide ion dikhata hai aur usse carbon ke peeche tak ek curved arrow, saath mein ek doosra curved arrow jo C–Cl bond ke electrons ko chlorine ki taraf jaate dikhata hai. Step 2 square brackets mein double dagger wala transition state hai: iodine aur chlorine dashed partial bonds se carbon se jude hain, har ek par δ− likha hai, aur baaki teen groups carbon se guzarte vertical plane mein hain. Step 3 product dikhata hai: left mein iodine juda hai, teen groups ab right ki taraf jhuke hain, aur right mein ek chloride ion door jaa raha hai.

Definition

SN2 reaction

Substitution, nucleophilic, bimolecular: ek-step reaction jismein bond banna aur tootna saath-saath hota hai, rate $= k [R X] [N u^{-}]$ hota hai aur configuration invert hoti hai.

Structure isliye matter karta hai kyunki nucleophile ko carbon ke peeche tak saaf raasta chahiye. Nucleophile ki taraf se dekho (Fig. 6.8) to methyl halide mein carbon lagbhag khula dikhta hai; hydrogen ki jagah aane wala har alkyl group use aur zyada chhupa deta hai. Isliye SN2 rates series $C H_{3} X$ > 1° > 2° >> 3° mein tezi se girte hain, aur tertiary halides practically is tarah react nahi karte. Ek carbon aage ki bheed bhi asar daalti hai: 1-bromo-2,2-dimethylpropane primary halide hai, phir bhi uska bulky neighbour back-side attack ko bahut slow kar deta hai.

3/4Do alkyl groups ek patla gap chhodte hain.

Fig. 6.8Nucleophile ki taraf se dekho to har methyl group target carbon ko aur zyada chhupata hai.NCERT Fig. 6.3 · p. 173

C–Cl bond ke seedhe along ek view, us side se jahan se nucleophile aayega: target carbon ek dashed circle ke beech mein hai, aur chlorine uske peeche chhupa hai. Right mein ek formula, uski class aur attack ki speed label wali ek horizontal bar. Step 1, chloromethane: carbon ke around teen chhote hydrogens, carbon poora khula, bar lambi aur tez likha hai. Step 2, chloroethane: ek hydrogen ki jagah ek bada methyl disc hai jo carbon ka upar wala hissa dhak leta hai; bar aadhi ho jaati hai, dheema. Step 3, 2-chloropropane: do methyl discs, bar kaafi chhoti. Step 4, 2-chloro-2-methylpropane: teen methyl discs carbon ko lagbhag chhupa dete hain, bar lagbhag gaayab, lagbhag 0.

SN1 mechanism

Tertiary halides substitute to karte hain, lekin doosre raaste se. 2-chloro-2-methylbutane, $C H_{3} C H_{2} C (C H_{3})_{2} C l$ , ko aqueous ethanol mein garam karo, to rate sirf halide ke concentration par depend karta hai: zyada hydroxide ions daalne se speed nahi badhti. Reaction first order hai. Is tarah ki reactions polar protic solvents mein sabse achhi chalti hain, jaise water aur alcohols, jinke O–H groups bante hue ions se hydrogen bond bana sakte hain.

SN1 rate law

rate = k [R - X]

(6.2)

Mechanism ke do steps hain. Pehle, slow step mein C–Cl bond khud tootta hai, dono electrons chlorine ke paas jaate hain, aur ek carbocation aur ek chloride ion bante hain. Bond todne mein energy lagti hai; iska bada hissa solvation se wapas mil jaata hai, jab protic solvent molecules chloride ion se hydrogen bond banate hain aur cation ke around jama ho jaate hain. Doosre, fast step mein ek nucleophile, aksar solvent molecule, carbocation se bond banata hai. Slow step mein sirf halide hissa leta hai, isliye rate law mein sirf uska concentration aata hai.

Steps (water attack karta hai, phir H⁺ khota hai)

\begin{aligned} R_{3} C - C l \overset{s l o w}{\to} \\ R_{3} C^{+} + C l^{-} \\ R_{3} C^{+} + H_{2} O \overset{f a s t}{\to} \\ R_{3} C - O H + H^{+} \end{aligned}

jahan

$R_{3} C$: 2-methylbutan-2-yl group, $(C H_{3})_{2} (C_{2} H_{5}) C$

2/4C–Br tootta hai: ek planar carbocation banta hai, jiske teen groups ke plane ke upar aur neeche ek khaali p orbital hai.

Fig. 6.9Flat carbocation par kisi bhi face se attack ho sakta hai.

Upar wala hissa ek energy profile hai: curve slow step label wali ek oonchi pehli peak tak chadhti hai, carbocation label wali ek uthli valley mein girti hai, fast label wali ek chhoti doosri peak par chadhti hai, aur products tak gir jaati hai. Ek dot current point dikhata hai. Neeche wala hissa har step ke structures dikhata hai. Step 1: ek tertiary carbon jiske methyl, ethyl aur propyl groups left ki taraf jhuke hain aur right mein bromine juda hai; dot shuru mein hai. Step 2: bromide door chala gaya hai aur carbon ek flat cation hai jis par + hai aur left-right do dashed lobes hain; dot valley mein hai. Step 3: hydroxide ions dono taraf se cation ke paas aate hain; dot doosri peak par hai. Step 4: do products, ek mein OH left mein aur groups right ki taraf jhuke, doosre mein OH right mein aur groups left ki taraf jhuke, label 50 : 50; dot end par hai.

Definition

SN1 reaction

Substitution, nucleophilic, unimolecular: R–X ka dheere ionise hokar carbocation banna, phir nucleophile dwara fast capture; rate $= k [R X]$ .

Definition

Carbocation

Ek ion jiske positively charged carbon ke sirf teen bonds aur chhe valence electrons hote hain; yeh $s p^{2}$ -hybridised aur planar hota hai.

Kyunki ionisation slow step hai, jo bhi cheez carbocation ko stable karti hai woh poori reaction ko tez kar deti hai. Alkyl groups electron density ko positive carbon ki taraf dhakelte hain (apne inductive effect aur hyperconjugation se), isliye cation stability ka order hai 3° > 2° > 1° > $C H_{3}^{+}$ . SN1 reactivity bhi isi order mein chalti hai, 3° > 2° > 1° > methyl: SN2 order ka bilkul ulta.

Allylic aur benzylic halides khaas taur par aasaani se ionise hote hain, primary hone par bhi, kyunki cation ka positive charge resonance se baant jaata hai. Allyl cation mein yeh dono end carbons par phaila hota hai; benzyl cation mein yeh $C H_{2}$ group ke saath-saath teen ring carbons tak pahunchta hai.

Allyl cation

\begin{aligned} C H_{2} = C H C H_{2}^{+} \overset{}{\leftrightarrow} \\ _{}^{}_{}^{+} C H_{2} C H = C H_{2} \end{aligned}

Sirf halogen badalne se dono mechanisms ek hi direction mein badalte hain: iodides sabse tez react karte hain aur fluorides lagbhag bilkul nahi, $R - I$ > $R - B r$ > $R - C l$ >> $R - F$ . Yahan do baatein milti hain. Chaaron mein C–I bond sabse weak hai, aur iodide ion, jo itna bada hai ki apna charge patla phaila sake, nikalne wala sabse stable halide ion hai.

Compare

SN2 aur SN1 aamne-saamne

SN2

ek step, koi intermediate nahi
rate $= k [R X] [N u^{-}]$ (second order)
back-side attack; configuration ka inversion
$C H_{3} X$ aur 1° ke liye sabse tez
achhe concentration mein strong nucleophile isse favour karta hai

SN1

carbocation se hokar do steps
rate $= k [R X]$ (first order)
kisi bhi face par attack; racemisation
3°, allylic aur benzylic ke liye sabse tez
polar protic solvents aur weak nucleophiles isse favour karte hain

Example 6.6NCERT Example 6.6 · p. 174

SN2 se kaun tez react karta hai?

Har pair mein kaunsa compound SN2 raaste se nucleophile ke saath tez react karta hai? Wajah batao.

$C H_{3} C H_{2} C H_{2} C l$ ya $(C H_{3})_{2} C H C l$
$C H_{3} C H_{2} C H_{2} C H_{2} C l$ ya $C H_{3} C H_{2} C H_{2} C H_{2} I$

Pehle khud try karo. Phir solution ek-ek step karke kholo.

Example 6.7NCERT Example 6.7 · p. 174

Dono mechanisms se ranking

Har set ko SN1 aur SN2 ki taraf reactivity ke order mein arrange karo.

$C H_{3} C l$ , $C H_{3} C H_{2} C l$ , $(C H_{3})_{2} C H C l$ , $(C H_{3})_{3} C C l$
$C_{6} H_{5} C H_{2} C l$ , $C_{6} H_{5} C H (C H_{3}) C l$ , $C_{6} H_{5} C (C H_{3})_{2} C l$

Pehle khud try karo. Phir solution ek-ek step karke kholo.

InteractiveSubstitution lab: SN1 ya SN2?

Buttons se substrate (methyl, primary, secondary, tertiary ya benzylic bromide), nucleophile (strong, jaise hydroxide ya cyanide, ya weak, jaise water) aur solvent (polar protic, jaise water ya ethanol, ya acetone) chune jaate hain. Do horizontal bars ek illustrative logarithmic scale par compare karti hain ki SN2 aur SN1 raaste kitne tez honge, aur ek line jeetne wale raaste ka naam batati hai. Ek energy-profile graph ek-hump wala SN2 curve aur do-hump wala SN1 curve banata hai, jinki heights usi scale ko follow karti hain. Ek mechanism panel reacting carbon ko uske teen groups ke saath dikhata hai aur learner ko jeetne wale mechanism ko step-by-step ya play karke dekhne deta hai: SN2 ke liye back-side attack aur umbrella inversion, ya SN1 ke liye flat carbocation tak ionisation aur dono faces se attack. Aakhri line chiral starting halide ke liye stereochemical result batati hai aur warning deti hai jab strong base uski jagah elimination karwa dega.

Fig. 6.10Ek halide, ek nucleophile aur ek solvent chuno, phir conditions jis mechanism ko favour karti hain use step-by-step ya play karke dekho.

Try karke dekho

Silver nitrate ke saath halides ki race

Tumhe chahiye

ethanolic silver nitrate solution (lagbhag 2 %)
1-chlorobutane, 1-bromobutane, 1-iodobutane aur 2-chloro-2-methylpropane
chaar test tubes, ek dropper aur garam paani wala ek beaker
ek stopwatch

Pehle guess karo

Teen straight-chain butyl halides mein se kaunsa sabse pehle precipitate dega?

1-chlorobutane1-bromobutane1-iodobutane

Kaunsa chloride jaldi cloudy hoga?

1-chlorobutane2-chloro-2-methylpropanedono ek saath

Chaar test tubes, har ek mein 1 mL ethanolic silver nitrate, garam paani (lagbhag 320 K) wale beaker mein khadi karo.
Har tube mein ek hi pal mein alag halide ki 3 boondein daalo aur timer shuru karo.
Note karo ki har tube kis time par cloudy hoti hai, aur precipitate ka colour kya hai.

Table 6.8Observations

Halide	Time (s), rang
1-Chlorobutane
1-Bromobutane
1-Iodobutane
2-Chloro-2-methylpropane

Tumhari entries apne aap save hoti hain.

Optical activity

Substitution teen dimensions mein kya karta hai, yeh samajhne ke liye humein stereochemistry ke kuch ideas chahiye. Saadharan light ek wave hai jiska electric field beam ke right angle par har direction mein vibrate karta hai. Polariser, jaise calcite se kata Nicol prism ya Polaroid sheet, sirf ek plane ki vibrations ko jaane deta hai: bahar nikalne wali light plane-polarised hoti hai.

Kisi suitable compound ka solution polarimeter (Fig. 6.11) ki tube mein daalo, to tube se nikalne wali light ab apne original plane mein vibrate nahi karti. Plane ek angle se ghoom gaya hai, jise tum analyser ko tab tak ghumakar naapte ho jab tak light phir se sabse bright na ho jaaye. Jo substances aisa karte hain unmein optical activity hoti hai. Agar lamp ki taraf dekhte hue tumhe analyser clockwise ghumana pade, to substance dextrorotatory hai, label (+) ya d; anticlockwise ka matlab laevorotatory, (−) ya l. Sign angle ke aage lagta hai, jaise +12° ya −12°.

3/4Chiral solution us plane ko angle α se ghuma deta hai.

Fig. 6.11Analyser ko tab tak ghumaya jaata hai jab tak light phir se sabse bright na ho; jitna angle ghuma, wahi rotation hai.NCERT 6.7.1 (c)(i) · p. 175

Left mein ek lamp beam ko polariser, sample tube aur analyser se hokar right mein ek aankh tak bhejta hai; beam ke neeche chhote circles end-on dekhi vibration ki direction dikhate hain. Step 1: lamp ki light saare planes mein vibrate karti hai, jo teen crossed lines se dikhaya gaya hai. Step 2: polariser ke baad sirf vertical vibration bachti hai. Step 3: tube chiral solution se bhar jaati hai aur usse nikalne wali vibration angle alpha se jhuki hai; analyser ke aage beam halki hai kyunki analyser abhi bhi vertical hai. Step 4: analyser ko alpha se clockwise ghumaya jaata hai jab tak light bright hokar na aaye, aur reading +α dikhayi jaati hai.

Definition

Optical activity

Kisi substance dwara plane-polarised light ke plane ka rotation; source ki taraf dekhte hue clockwise ke liye (+) aur anticlockwise ke liye (−).

Chirality aur enantiomers

Timeline

Mudi hui light se 3D molecules tak

1815
Light ghumane wale liquids
Jean-Baptiste Biot paate hain ki sugar solutions aur turpentine plane-polarised light ko ghumate hain.
1848
Mirror-image crystals
Louis Pasteur haath se tartrate crystals ko do mirror-image shapes mein alag karte hain; unke solutions light ko barabar lekin ulti directions mein ghumate hain.
1874
Tetrahedral carbon
J. H. van 't Hoff aur J. A. Le Bel alag-alag ise tetrahedron ke corners ki taraf point karte chaar bonds se samjhate hain.
1901
Pehla Nobel Prize
Van 't Hoff ko solutions aur reaction rates par unke kaam ke liye Chemistry ka pehla Nobel Prize milta hai.

Right chappal left pair mein fit nahi hogi, chahe tum use kaise bhi ghumao, jabki har chappal doosri ki mirror image hai. Jo object apni mirror image par superimpose nahi ho sakta woh chiral hai; yeh word haath ke liye Greek word se aaya hai, jo iska sabse jaana-pehchana example hai. Cricket ball, steel ka glass ya bina chheeli pencil apne reflection se poori tarah mel khaati hai aur achiral hai. Molecules bhi yahi test maante hain: chiral molecules optically active hote hain, achiral nahi.

Chirality ki sabse common wajah hai chaar alag groups se juda carbon atom, jise stereocentre (ya asymmetric carbon) kehte hain. Iske chaar bonds tetrahedron ke corners ki taraf point karte hain, isliye groups do mirror-image tarikon se arrange ho sakte hain. Kisi molecule ko test karne ke liye use uski mirror image ke bagal mein banao (ya model banao), image ko poora ghumao aur dekho ki kya woh original se mel kha sakti hai (Fig. 6.12). 2-chloropropane mein beech wale carbon par do same methyl groups hain, aur aadha ghumaav image ko bilkul fit kar deta hai. 2-chlorobutane mein C2 par H, Cl, $C H_{3}$ aur $C_{2} H_{5}$ hain, aur koi bhi ghumaav image ko fit nahi kar sakta.

4/4Aadhe ghumaav ke baad ethyl aur methyl galat sides par hain. Chiral.

Fig. 6.12Mirror image banao, use ghumao, aur original ke upar rakhne ki koshish karo.NCERT Figs. 6.5–6.6 · p. 176

Ek dashed vertical mirror figure ko baant deta hai. Step 1: left mein 2-chloropropane, H upar, Cl plane mein neeche-left, ek methyl wedge par aur ek dash par; right mein uski mirror image. Step 2: mirror image ko vertical axis ke around aadha ghumaya jaata hai, jo curved arrow se dikhaya gaya hai, aur ab woh original se bilkul match karti hai; ek green panel par identical: achiral likha hai. Step 3: 2-chlorobutane ke liye wahi layout, wedge par methyl aur dash par ethyl, aur uski mirror image. Step 4: ghumayi gayi image mein ethyl wedge par aur methyl dash par hai; dashed rings mismatched wedge groups ko mark karte hain aur ek panel par not identical: chiral likha hai.

Definition

Chiral

Aisa object ya molecule jo apni mirror image par superimpose nahi ho sakta; iska ulta achiral hai.

ExampleTumhara haath; 2-chlorobutane.

Definition

Stereocentre (asymmetric carbon)

Chaar alag atoms ya groups se juda carbon atom.

Example2-chlorobutane ka C2: H, Cl, $C H_{3}$ , $C_{2} H_{5}$ .

InteractiveChirality explorer

Chaar drop-down menus tetrahedral carbon par groups set karte hain, jo H, CH3, C2H5, OH, F, Cl, Br, I aur COOH mein se chune jaate hain, aur 2-chlorobutane, 2-chloropropane, bromochlorofluoromethane, lactic acid aur dichloromethane ke presets bhi hain. Molecule left mein bana hai, do bonds plane mein, ek wedge aur ek dash, aur uski mirror image dashed mirror ke right mein. Turn button mirror image ko smoothly ghumata hai; agar koi aisa ghumaav hai jo use molecule par bilkul rakh de to wahi chunta hai, warna aadha ghumaav jo upar aur left wale groups ko jagah par rakhe; Reset button image ko wapas laata hai. Result line batati hai ki ghumayi image original se match karti hai ya nahi, jagah se hate groups ko ring karke unke naam batati hai, aur batati hai ki carbon stereocentre hai ya nahi aur molecule chiral hai ya nahi. Swap button wedge aur dash groups ko badal deta hai, yeh dikhane ke liye ki stereocentre par do groups badalne se mirror-image arrangement banti hai.

Fig. 6.13Ek carbon ke liye chaar groups chuno, uski mirror image banao, use ghumao aur dekho ki dono match karte hain ya nahi.

Chalo explore karein

Ek stereocentre banao

Tumhe chahiye

chaar rangon mein clay ya plasticine
toothpicks
ek mirror

Pehle guess karo

Chaar alag balls ke saath, kya model aur uska mirror-image model kabhi match karenge?

nahi, kabhi nahihaan, sahi ghumaav ke baadsirf tab jab tum unhe upar se dekho

Carbon ke liye clay ki ek badi ball banao aur usmein chaar toothpicks aise ghusao ki woh tetrahedron ke corners ki taraf point karein (camera tripod ki tarah, jiski ek taang seedhe upar ho).
Toothpicks par alag-alag rangon ki chaar chhoti balls lagao.
Model ko mirror ke saamne rakho aur ek doosra model banao jo reflection se match kare.
Har mumkin tareeke se ek model ko doosre ke upar bilkul fit karne ki koshish karo.
Ab har model par do balls ko same rang ka kar do aur phir se try karo.

Do stereoisomers jo non-superimposable mirror images hain, enantiomers ka ek pair banate hain. Pair ke dono members ke melting points, boiling points, densities ya refractive indices naapo to same numbers milte hain; saadharan achiral reagents ke saath woh same rate se react bhi karte hain. Unhe polarimeter alag pehchanta hai: dono plane-polarised light ko bilkul same angle se ghumate hain, ek clockwise aur doosra anticlockwise. Lekin labels ke saath sambhal kar. Compound (+) hai ya (−), yeh experiment se pata chalta hai; ise space mein uski arrangement, yaani uski configuration, ki wedge-and-dash drawing se nahi padha ja sakta.

Definition

Enantiomers

Stereoisomers ka ek pair jo non-superimposable mirror images hain; unke optical rotations barabar aur ulte hote hain.

Example(+)- aur (−)-2-chlorobutane.

Agar kisi sample mein dono enantiomers barabar maatra mein hon to? Light ko ek taraf ghumane wale har molecule ke liye ek partner hai jo use wapas ghuma deta hai, isliye net rotation zero hai. Aisa 50 : 50 sample racemic mixture (ya racemic modification) hai, jise prefix (±) ya dl se dikhate hain, jaise (±)-2-chlorobutane. Koi bhi process jo ek akele enantiomer ko is mixture mein badal de, racemisation kehlata hai.

Definition

Racemic mixture

Do enantiomers ka equimolar (50 : 50) mixture; yeh optically inactive hota hai aur ise (±) label kiya jaata hai.

Example 6.8NCERT Example 6.8 · p. 177

Chiral molecules pehchanna

Har pair mein kaunsa molecule chiral hai? Stereocentre dhoondhkar apna choice justify karo.

$C H_{3} C H_{2} C H (C l) C H_{2} C H_{3}$ aur $C H_{3} C H (C l) C H_{2} C H_{2} C H_{3}$
$C H_{2} B r C l$ aur $C H_{3} C H B r C l$
$(C H_{3})_{2} C H C H_{2} C H_{2} O H$ aur $C H_{3} C H_{2} C H (C H_{3}) C H_{2} O H$

Pehle khud try karo. Phir solution ek-ek step karke kholo.

Retention, inversion aur racemisation

Stereocentre par kya hota hai, yeh is par depend karta hai ki uske chaar bonds mein se koi tootta hai ya nahi. Agar koi nahi tootta, to groups apni arrangement banaye rakhte hain: retention of configuration. Optically active 1-bromo-3-methylpentane, $B r C H_{2} C H_{2} C H (C H_{3}) C H_{2} C H_{3}$ , lo, jiska stereocentre C3 hai. Acetone mein sodium iodide ke saath garam karne par yeh C1 par Br ko I se badalta hai, jo do carbons door hai, isliye stereocentre ko koi chhoota hi nahi aur bane 1-iodo-3-methylpentane ki C3 par same arrangement rehti hai. Lekin uske rotation ka sign bromide jaisa ho, yeh zaroori nahi: yeh ek alag compound hai jiska apna rotation hai, jo kisi bhi sign ka ho sakta hai.

Agar stereocentre ka koi bond toote aur naya group Y, X ki jagah le, to teen possible outcomes hain, jo neeche diye hain.

Compare

Stereocentre par Y ke X ko replace karne par teen outcomes

Retention

Y wahi position leta hai jo X ki thi
product ki configuration reactant jaisi hi hai

Inversion

Y X ki ulti side se aata hai
baaki teen groups umbrella ki tarah palat jaate hain
product ki configuration ulti hai

Racemisation

dono arrangements bante hain, 50 : 50
product koi optical rotation nahi dikhata

SN2 inversion deta hai. Nucleophile hamesha leaving group ki ulti side se aata hai, isliye configuration palat jaati hai. Jab 2-chlorobutane ka optically active sample acetone mein sodium iodide ke saath react karta hai, to bane 2-iodobutane ki configuration inverted hoti hai. Har molecule mein iodine us face ke opposite face par aata hai jahan se uska chlorine nikla tha.

SN1 (lagbhag) racemisation deta hai. Leaving group ke jaane ke baad flat carbocation ko original arrangement yaad nahi rehti: yeh achiral hai, aur nucleophile uske upar wale ya neeche wale face se barabar aasaani se bond bana sakta hai. Isliye aqueous ethanol mein optically active 3-bromo-3-methylhexane lagbhag racemic 3-methylhexan-3-ol deta hai. Practice mein aksar inverted product thoda zyada hota hai, kyunki ek pal ke liye nikalta hua bromide ion us face ko dhake rehta hai jahan se woh nikla.

Elimination reactions

Haloalkane mein halogen wala carbon α-carbon hai aur usse juda koi bhi carbon β-carbon hai. Aise halide ko strong base ke saath garam karo, aam taur par ethanol mein ghula potassium hydroxide (alcoholic KOH), to do cheezein saath-saath hoti hain: base β-carbon se ek proton kheench leta hai aur halide ion α-carbon se nikal jaata hai. Peeche bache electrons dono carbons ke beech C=C double bond banate hain. Kyunki H aur X ek pair ki tarah nikalte hain, is reaction ko dehydrohalogenation kehte hain, aur kyunki hydrogen β position se aata hai, ise β-elimination bhi kehte hain.

Dehydrohalogenation (alcoholic KOH, heat; KX aur H₂O bhi bante hain)

\begin{aligned} R C H_{2} C H_{2} X \overset{K O H}{\to} \\ R C H = C H_{2} \end{aligned}

Definition

β-Elimination

Aisi reaction jismein β-carbon se H aur bagal wale α-carbon se X hatta hai, aur C=C bond banta hai.

Example1-Bromopropane aur alcoholic KOH se propene banta hai.

Kai halides mein do ya zyada alag β-carbons par hydrogens hote hain, isliye ek se zyada alkene ban sakte hain, phir bhi aam taur par ek product haavi rehta hai. 1875 mein Kazan mein kaam karte hue Alexander Zaitsev ne pattern pakda: main product woh alkene hota hai jiske double-bond carbons par sabse zyada alkyl groups hon. Aise highly substituted alkenes zyada stable hote hain, aur unki taraf jaane wale raaste ka energy barrier kam hota hai (Fig. 6.14).

4/4Zyada substituted alkene major product hai.

Fig. 6.14Zyada substituted alkene major product hai (Zaitsev rule).NCERT 6.7.1 (2) · p. 180

Condensed structure CH3–CH(Br)–CH(CH3)–CH3 dikhaya gaya hai; bromine wale carbon par alpha aur dono neighbouring carbons par beta tag hai. Step 1 sirf tags dikhata hai. Step 2 terminal CH3 aur Br ko ring karta hai aur neeche-left CH2=CH–CH(CH3)2, 3-methylbut-1-ene, tak arrow banata hai, jiske C=C par ek alkyl group hai. Step 3 branched CH aur Br ko ring karta hai aur neeche-right CH3–CH=C(CH3)2, 2-methylbut-2-ene, tak arrow banata hai, jiske C=C par teen alkyl groups hain. Step 4 dono products dikhata hai, kramashah minor aur major label ke saath.

Example

Zaitsev rule lagana

3-Bromo-3-methylpentane, $C H_{3} C H_{2} C (B r) (C H_{3}) C H_{2} C H_{3}$ , ko alcoholic KOH ke saath garam kiya jaata hai. Possible alkenes aur major alkene ke naam batao.

Pehle khud try karo. Phir solution ek-ek step karke kholo.

Key ideaNCERT Elimination banaam substitution · p. 180

Elimination ya substitution?

Har base ek potential nucleophile bhi hai, isliye jab bhi haloalkane kisi base se milta hai, substitution aur elimination mein muqabla hota hai, aur jo tez ho wahi main product tay karta hai. Size matter karta hai: bulky base ke liye molecule ke kinare se ek khula hydrogen kheenchna carbon tak ghusne se kahin aasaan hai, isliye woh eliminate karne ki taraf jhukta hai. Heat aur aqueous ki jagah alcoholic solvent bhi isi taraf dhakelte hain. Halide ka structure bhi matter karta hai:

Table 6.9Typical outcomes

Halide	Conditions	Result
$C H_{3} X$ ya 1°	achha nucleophile ( $I^{-}$ , $C N^{-}$ , aqueous $O H^{-}$ )	SN2
1°	bulky strong base, jaise $(C H_{3})_{3} C O - K^{+}$ , heat	elimination
2°	ethanol mein strong base, heat	mainly elimination
2°	achha nucleophile jo weak base hai	SN2
3°	water ya ethanol, koi strong base nahi	SN1 (thoda elimination)
3°	strong base (alcoholic KOH)	elimination

Isse results ka ek classic pair samajh aata hai. Aqueous KOH ke saath haloalkane mainly alcohol deta hai: water mein hydroxide ion hydrogen-bonded water molecules se ghira rehta hai, jo use base ke roop mein kamzor karta hai par achha nucleophile rehne deta hai. Garam karne par alcoholic KOH ke saath medium mein ethoxide ions, $C_{2} H_{5} O^{-}$ , hote hain, jo zyada strong aur kam solvated base hain, isliye alkene tak elimination jeet jaata hai.

Metals ke saath reaction

Carbon ke chlorides, bromides aur iodides kai metals ke saath react karke organometallic compounds dete hain, jinmein carbon seedha metal se juda hota hai. Sabse kaam ke alkyl- aur arylmagnesium halides, RMgX, hain, jinhe pehli baar 1900 mein French chemist Victor Grignard ne banaya aur unke naam par inhe Grignard reagents kehte hain. Ise banane ke liye magnesium turnings ko dry diethyl ether mein halide ke saath hilaya jaata hai; ether molecules magnesium se bond banakar reagent ko solution mein rakhte hain.

Grignard reagent banana

\begin{aligned} C_{2} H_{5} B r + M g \\ \overset{d r y e t h e r}{\to} C_{2} H_{5} M g B r \end{aligned}

RMgX banane se carbon ki polarity ulat jaati hai. R–X mein carbon δ+ hai, lekin magnesium carbon se kaafi kam electronegative hai, isliye R–MgX mein shared electrons carbon ki taraf jhukte hain aur woh δ− ban jaata hai; Mg–X bond lagbhag ionic hai. δ− carbon ek powerful base hai. Use water, alcohol ya amine ka O–H ya N–H proton do, aur woh use turant le leta hai, peeche hydrocarbon R–H chhod kar. Isiliye Grignard reagents dry ether mein, dhyaan se sukhaye glassware mein banaye jaate hain. Chemists is reactivity ko jaan-boojhkar bhi use karte hain: water daalne se halide saaf-saaf alkane mein badal jaata hai, aur heavy water ( $D_{2} O$ ) deuterium atom ko theek wahin rakhta hai jahan halogen tha.

Water Grignard reagents ko khatam kar deta hai

\begin{aligned} R M g X + H_{2} O \overset{}{\to} \\ R H + M g (O H) X \end{aligned}

Definition

Grignard reagent

Ek organomagnesium halide $R M g X$ , jo dry ether mein R–X aur Mg se banta hai; iska δ− carbon strong base aur nucleophile ki tarah kaam karta hai.

Wurtz reaction. Dry ether mein sodium do alkyl groups ko bhi jod sakta hai: haloalkane ke do molecules apne halogens metal ko de dete hain, aur unke alkyl groups R–R ke roop mein jud jaate hain. Yeh method sirf ek halide ke liye theek hai, kyunki do alag haloalkanes ka mixture teen alag alkanes deta hai.

Wurtz reaction

\begin{aligned} 2 R X + 2 N a \\ \overset{d r y e t h e r}{\to} R - R \\ + 2 N a X \end{aligned}

Practice · 2 questions

Practice: haloalkanes ki reactions: answers ke saath

1
Short answerMediumNCERT Intext Questions 6.7–6.8
Har pair mein woh compound chuno jo diye gaye mechanism se tez react karta hai, aur ek wajah batao.
1. SN2: $C H_{3} C H_{2} C H_{2}$ – $C H_{2} C H_{2} C l$ ya $C H_{3} C H_{2}$ – $C H (C l) C H_{2} C H_{3}$
  Solution dikhao
  1-Chloropentane: primary hai, isliye iski back side secondary 3-chloropentane se kam bheed wali hai.
2. SN2: $C H_{3} (C H_{2})_{5} I$ ya $(C H_{3} C H_{2})_{2} C H C H_{2} I$
  Solution dikhao
  1-Iodohexane. Dono primary hain, lekin 1-iodo-2-ethylbutane mein β-carbon se do ethyl groups latke hain, reacting carbon ke bilkul bagal mein, aur raasta bhar dete hain.
3. SN1: $(C H_{3})_{2} C (C l)$ – $C H_{2} C H_{2} C H_{3}$ ya $C H_{3} C H (C l)$ – $C H_{2} C H_{2} C H_{3}$
  Solution dikhao
  2-Chloro-2-methylpentane: yeh ionise hokar tertiary carbocation banata hai, jo 2-chloropentane se bane secondary carbocation se zyada stable hai.
4. SN1: $C H_{3} C H_{2} C H_{2} C H_{2} C l$ ya $C_{6} H_{5} C H_{2} C l$
  Solution dikhao
  Benzyl chloride: iska cation ring ke saath resonance se stable hota hai.
2
Short answerHardNCERT Intext Question 6.9
A, B, C aur D pehchano.
1. Bromocyclopentane + Mg (dry ether) → A; A + $H_{2} O$ → B
  Solution dikhao
  A = cyclopentylmagnesium bromide, $C_{5} H_{9} M g B r$ ; B = cyclopentane, $C_{5} H_{10}$ .
2. Ek halide $R - X$ dry ether mein Na ke saath 2,5-dimethylhexane deta hai. Dry ether mein Mg ke saath yeh C deta hai, aur C water ke saath D deta hai. R–X, C aur D pehchano.
  Solution dikhao
  2,5-Dimethylhexane $(C H_{3})_{2} C H C H_{2}$ – $C H_{2} C H (C H_{3})_{2}$ hai, yaani do isobutyl groups jude hue. Isliye R–X 1-bromo-2-methylpropane, $(C H_{3})_{2} C H C H_{2} B r$ (ya chloride/iodide) hai; C = $(C H_{3})_{2} C H$ – $C H_{2} M g B r$ ; D = 2-methylpropane, $(C H_{3})_{3} C H$ .

6.7.2 Haloarenes ki reactions

Nucleophilic substitution

Chloroethane ko aqueous sodium hydroxide ke saath reflux karo to jaldi hi ethanol mil jaata hai; chlorobenzene ke saath yahi karo to tumhe chlorobenzene hi wapas milta hai. Ring par (aur C=C carbon par) lage halogens nucleophiles ko bhaav nahi dete, aur C–X bond ke chaar features iski wajah samjhate hain:

Bond kuch had tak double hai. Chlorine ka ek lone pair ring ke π electrons ke saath overlap karta hai, jisse aise resonance structures bante hain jinmein $C = C l^{+}$ hota hai. Asli C–Cl bond single aur double ke beech kahin hai, aur use todna zyada mushkil hai.
$s p^{2}$ carbon. $s p^{2}$ orbital mein 33 % s character hota hai, $s p^{3}$ mein 25 %, isliye ring carbon bonding pair ko zyada paas pakadta hai. C–Cl bond chhota aur mazboot hai: chlorobenzene mein lagbhag 174 pm, jabki chloromethane mein lagbhag 178 pm.
Koi stable cation nahi. Agar C–X bond ionise ho bhi jaaye, to phenyl cation ka khaali orbital ring ke plane mein hoga, jahan π electrons pahunch nahi sakte. Resonance ki madad ke bina yeh bahut unstable hai, isliye SN1 raasta band hai.
Peeche se ghusne ka raasta nahi. C–X bond ki back side ring ke andar point karti hai, aur electron-rich π cloud paas aate nucleophile ko repel karta hai, isliye SN2 raasta bhi band hai.

2/3Cl ka lone pair ring mein delocalise hota hai: chhota, kuch had tak double C–Cl bond.

Fig. 6.15Partial double-bond character, sp² carbon aur raaste mein ring, teeno C–Cl bond ko bachate hain.NCERT 6.7.2 (1) · p. 181

Left mein chlorobenzene aur right mein chloromethane bane hain, dono mein chlorine par teen lone pairs. Cl wale ring carbon par sp2 aur chloromethane ke carbon par sp3 likha hai. Step 1 sirf dono molecules dikhata hai. Step 2 chlorobenzene mein chlorine ke lone pair se ring bond ki taraf ek curved arrow, C aur Cl ke beech partial double-bond character dikhane wali ek dashed doosri line, aur bond lengths, chlorobenzene ke liye 174 pm aur chloromethane ke liye 178 pm, jodta hai. Step 3 har molecule ke neeche se aata nucleophile arrow dikhata hai: chlorobenzene ke neeche woh ring par blocked likhi bar par ruk jaata hai, jabki chloromethane ke neeche woh carbon tak pahunchta hai, jahan open likha hai.

Hydroxyl se replacement. Kaafi zor lagaya jaaye to substitution hota hai: chlorobenzene ko lagbhag 300 atm par 600 K se upar aqueous NaOH ke saath garam karne par sodium phenoxide banta hai, jo acidify karne par phenol deta hai. Kahin naram raasta hai halogen ke ortho ya para par nitro group (ya koi aur strong electron-withdrawing group) lagana. Har aisa group reaction ko kaafi aasaan bana deta hai, jaisa table dikhati hai, jabki halogen ke meta par nitro group mushkil se madad karta hai.

Table 6.10Cl ko OH se replace karna kitna mushkil hai?

Chloroarene	Kya chahiye
chlorobenzene	high pressure par 600 K se upar NaOH(aq)
1-chloro-3-nitrobenzene	lagbhag utna hi mushkil: meta NO₂ mushkil se madad karta hai
1-chloro-4-nitrobenzene	garam NaOH(aq), lagbhag 430 K (4-nitrophenol ka ek industrial raasta)
1-chloro-2,4-dinitrobenzene	ubalta aqueous sodium carbonate, lagbhag 373 K
2-chloro-1,3,5-trinitrobenzene	sirf garam paani

Wajah mechanism mein hai, jo ek addition ke baad elimination hai. Slow pehle step mein hydroxide chlorine wale carbon par judta hai. Woh carbon $s p^{3}$ ban jaata hai, ring apna aromatic sextet kho deti hai, aur us par ek negative charge aata hai jise resonance attack site ke ortho aur para carbons par phaila deta hai. Fast doosre step mein chloride nikal jaata hai aur aromatic ring wapas aa jaati hai. In ortho ya para positions mein se kisi par baitha nitro group negative charge ko apne oxygen atoms par kheench sakta hai, jisse intermediate stable hota hai aur barrier kam hota hai. Meta position se woh charge se kabhi milta hi nahi (Fig. 6.16).

3/5Para (ya ortho) NO₂ charge ka kuch hissa apne oxygens par kheench leta hai.

Fig. 6.16Halogen ke ortho ya para par nitro group negative charge ka kuch hissa utha sakta hai; meta nitro group nahi.NCERT 6.7.2 (1) · p. 183

Ek benzene ring jiske upar Cl aur neeche NO2 hai, label 4-nitro isomer. Step 1: ek OH⁻ ion Cl wale carbon ke paas aata hai. Step 2: OH aur Cl dono us carbon par hain, ring ke andar wala circle ek dashed arc se badal jaata hai, aur uske bagal ke do carbons aur neeche wale carbon par minus-sign bubbles aate hain. Step 3: NO2 group par ek extra minus bubble aata hai, jo dikhata hai ki woh charge share karta hai. Step 4: Cl⁻ nikal gaya, ring par sirf OH bacha aur aromatic circle wapas aa gaya. Step 5: left wali ring step 3 wali picture rakhti hai, aur right mein ek doosri ring, 3-nitro isomer, aati hai jismein NO2 neeche ki ek side wale carbon par hai; uske minus bubbles baaki carbons par aate hain, NO2 wale par kabhi nahi.

Electrophilic substitution

Haloarene ki ring abhi bhi benzene ki jaani-pehchani electrophilic substitutions (nitration, halogenation, sulphonation aur dono tarah ki Friedel–Crafts reaction) mein hissa leti hai, lekin halogen details badal deta hai. Iski electronegativity σ bond ke through ring se electron density kheench leti hai (−I effect), isliye electrophiles benzene ke muqable dheere attack karte hain aur zyada strong conditions chahiye hoti hain. Lekin iske lone pairs ring ke saath share ho sakte hain (+R effect), aur yeh madad tabhi milti hai jab electrophile ne ortho ya para carbon par attack kiya ho (Fig. 6.17). Nateeja anokha hai: ek group jo ring ko deactivate karta hai, phir bhi naye aane walon ko ortho aur para bhejta hai, zyaadatar para, jahan zyada jagah hai.

3/3Ortho jaisa, lekin zyada jagah ke saath: main product.

Fig. 6.17Sirf ortho aur para attack positive charge ko chlorine ke bagal mein laate hain, jahan uska lone pair use share kar sakta hai.NCERT 6.7.2 (2) · p. 184

Chlorobenzene, jiske upar Cl aur uske lone pairs hain. Har step mein electrophile E aur ek hydrogen attack hue ring carbon par bane hain, aur plus-sign bubbles un teen ring carbons ko mark karte hain jo intermediate ka positive charge share karte hain. Step 1, ortho attack: ek bubble Cl wale carbon par aata hai aur chlorine ke bagal mein ek extra bubble dikhta hai; side panel par likha hai + C–Cl carbon tak jaata hai, Cl share karta, favoured. Step 2, meta attack: bubbles baaki teen carbons par aate hain aur C–Cl carbon par kabhi nahi; panel par likha hai + C–Cl carbon tak nahi jaata, Cl madad nahi, disfavoured. Step 3, para attack: ortho ki tarah, C–Cl carbon par ek bubble aur Cl ke bagal mein ek; favoured (major).

Table 6.11Bromobenzene ka electrophilic substitution (kuch ortho isomer bhi banta hai)

Reagents	Main product
nitration: conc. $H N O_{3}$ + conc. $H_{2} S O_{4}$	1-bromo-4-nitrobenzene
bromination: $B r_{2}$ , anhydrous $F e B r_{3}$	1,4-dibromobenzene
Friedel–Crafts acylation: $C H_{3} C O C l$ , anhydrous $A l C l_{3}$	1-(4-bromophenyl)ethan-1-one
Friedel–Crafts alkylation: $C H_{3} C H_{2} C l$ , anhydrous $A l C l_{3}$	1-bromo-4-ethylbenzene
sulphonation: conc. $H_{2} S O_{4}$ , heat	$p$ - $B r C_{6} H_{4} S O_{3} H$ , ek sulfonic acid

Example 6.9NCERT Example 6.9 · p. 185

Product ratio padhna

Chlorobenzene ka nitration lagbhag 30 % 1-chloro-2-nitrobenzene, 1 % 1-chloro-3-nitrobenzene aur 69 % 1-chloro-4-nitrobenzene deta hai, aur reaction benzene ke muqable lagbhag tees guna slow hai. Dono baatein samjhao.

Pehle khud try karo. Phir solution ek-ek step karke kholo.

Metals ke saath reaction

Wurtz–Fittig reaction. Dry ether mein sodium ek aryl group ko alkyl group se jod sakta hai: aryl halide aur alkyl halide ke mixture ko metal ke saath garam karo aur alkylbenzene banta hai. Fittig reaction. Sirf aryl halide ho to sodium do aryl groups ko jodkar biaryl deta hai.

Wurtz–Fittig: ethylbenzene

\begin{aligned} C_{6} H_{5} B r + C_{2} H_{5} B r \\ + 2 N a \overset{e t h e r}{\to} \\ C_{6} H_{5} C_{2} H_{5} + 2 N a B r \end{aligned}

Fittig: biphenyl

\begin{aligned} 2 C_{6} H_{5} B r + 2 N a \\ \overset{e t h e r}{\to} C_{6} H_{5} - C_{6} H_{5} \\ + 2 N a B r \end{aligned}

6.8 Polyhalogen Compounds

Ek ya do carbons par kai halogen atoms lagao aur tumhare paas polyhalogen compound hai. Inmein se kuch factories, kheton aur gharon ke liye million tonnes mein banaye gaye hain. Jin khoobiyon ne inhe aakarshak banaya, chemical stability aur fats aur oils ko dissolve karne ka hunar, wahi inmein se kai ko logon ke liye harmful aur environment se dheere gaayab hone wala bhi banati hain.

6.8.1 Dichloromethane (Methylene chloride)

Dichloromethane, $C H_{2} C l_{2}$ , organic substances ki ek bahut badi range ko dissolve karta hai, aasaani se aag nahi pakadta aur sirf lagbhag 313 K par ubalta hai, isliye jaldi evaporate hokar kuch peeche nahi chhodta. Yahi combination ise kai paint aur varnish strippers ka active ingredient aur pharmaceutical factories mein standard extraction solvent banata hai (kabhi ise coffee se caffeine nikalne mein bhi use kiya jaata tha). Yeh metal parts ki grease bhi saaf karta hai aur pehle aerosol sprays ko propel karne mein use hota tha.

Iske khatre isi volatility se aate hain. Iski bhaari vapour kam ventilation wale kamron mein jama ho jaati hai, aur use saans mein lena ek slow anaesthetic jaisa kaam karta hai. Log dizzy aur beemar mehsoos karte hain, unki ungliyon mein jhunjhunahat ya sunnpan aa sakta hai, aur kam levels bhi sunne aur dekhne ki shakti ko thoda kam kar sakte hain. Chheente skin ko jalate hain aur cornea ko nuksaan pahuncha sakte hain. Body mein liver iska kuch hissa carbon monoxide mein badal deta hai, jo blood ki oxygen supply kaat deta hai. Ise sirf achhe ventilation, gloves aur eye protection ke saath use kiya jaata hai.

6.8.2 Trichloromethane (Chloroform)

Chloroform, $C H C l_{3}$ , brown bottles mein bilkul gardan tak bharkar bikta hai, aur iski wajah chemical hai. Air aur light mein yeh dheere-dheere oxidise hokar phosgene (carbonyl chloride) ban jaata hai, jo ek bahut zehreeli gas hai. Andheri, poori bhari bottle light aur oxygen dono ko bahar rakhti hai, aur aam taur par lagbhag 1 % ethanol daala jaata hai taaki jo phosgene phir bhi bane woh khatam ho jaaye.

Chloroform se phosgene

\begin{aligned} 2 C H C l_{3} + O_{2} \\ \overset{l i g h t}{\to} 2 C O C l_{2} \\ + 2 H C l \end{aligned}

Aaj zyaadatar chloroform seedha use nahi hota balki chlorodifluoromethane, $C H C l F_{2}$ , mein badla jaata hai, jo refrigerant R-22 hai aur PTFE ka starting material bhi. Yeh waxes, rubber aur kai plant extracts ke liye ek useful laboratory solvent bana hua hai. Iski pehli shohrat medical thi: 1847 mein Edinburgh ke obstetrician James Young Simpson ne ise general anaesthetic ke roop mein introduce kiya. Doctors ne ise chhod diya kyunki sulane wali dose aur khatarnak dose ke beech ka fark bahut kam tha. Chloroform central nervous system ko sust karta hai (thodi der exposure ke baad neend aur sirdard), dil ki dhadkan ki rhythm bigaad sakta hai aur baar-baar exposure se liver aur kidneys ko nuksaan pahunchata hai; liver khud iska kuch hissa phosgene mein badal deta hai.

6.8.3 Triiodomethane (Iodoform)

Triiodomethane, $C H I_{3}$ , tez smell wala ek yellow crystalline solid hai. Aage ke chapters mein tum ise iodoform test ke yellow precipitate ke roop mein dekhoge. Unneesvi sadi ke surgeons ise zakhmon par chhidakte the, lekin yeh khud kabhi microbes ko nahi maarta tha: yeh dheere-dheere iodine chhodta tha, jo yeh kaam karta tha. Iski smell itni tikau thi ki iski jagah povidone–iodine jaisi bina smell wali iodine preparations aa gayin, jo aaj hospitals mein use hone wala brown antiseptic hai.

6.8.4 Tetrachloromethane (Carbon tetrachloride)

Tetrachloromethane, $C C l_{4}$ , dense hai, jalta nahi aur grease ko behtareen tarah se dissolve karta hai. Isliye beesvi sadi ke zyaadatar hisse mein yeh har jagah tha: fire extinguishers, dry cleaning, gharelu daag hatane wale products aur metal degreasing mein, aur CFC refrigerants aur aerosol propellants ke raw material ke roop mein. Do discoveries ne iske zyaadatar uses khatam kar diye.

Pehli, yeh ek gambhir zeher hai. Iski vapour nervous system ko dabaati hai: halke exposure se sirdard, chakkar aur ulti hoti hai, jabki zyada exposure se behoshi, dil ki dhadkan bigadna ya rukna aur maut ho sakti hai, kabhi-kabhi nerves ko lamba nuksaan bhi. Yeh liver ka bhi badnaam zeher hai, liver cancer se juda hai, aur aankhon mein jalan karta hai. Doosri, jo vapour nikal jaati hai woh bina badle stratosphere tak chadh jaati hai aur ozone ko nasht karti hai (Section 6.8.5). Tab se international agreements ne iska lagbhag saara production band karwa diya hai.

6.8.5 Freons

1920s mein ghar ke refrigerators ammonia, sulfur dioxide ya chloromethane par chalte the, jo sab toxic hain, aur leaks se maut hoti thi. 1928 mein Thomas Midgley aur unke saathiyon ne methane aur ethane ke chlorofluorocarbons (CFCs) mein ek safer jawaab dhoondha, jo freons ke naam se bike. Yeh gases non-toxic hain, jalti nahi, metals ko corrode nahi karti, lagbhag kisi se react nahi karti aur thode pressure par liquid ban jaati hain. Dashakon tak yeh refrigerators, air conditioners, aerosol cans aur plastic foams mein bhari rahin. Freon-12, $C C l_{2} F_{2}$ , tetrachloromethane se Swarts-type exchange dwara chlorine ko fluorine se badalkar banta hai.

Inki stability hi problem hai. Zameen par chhoda gaya freon molecule tootta nahi; kuch saalon mein woh oopar stratosphere tak pahunch jaata hai. Wahan hard ultraviolet light ek chlorine atom ko alag kar deti hai, jo reactions ki ek chain shuru karta hai jo ozone ko nasht karti hai, wahi layer jo Earth ko harmful UV se bachati hai (Fig. 6.18). Ek akela chlorine atom band hone se pehle hazaaron ozone molecules hata sakta hai.

4/4ClO ek O atom se milta hai, $O_{2}$ deta hai aur $C l \cdot$ ko phir se azaad kar deta hai: ek catalytic cycle.

Fig. 6.18Chlorine atom har cycle se bina badle nikalta hai, aur ozone nasht karne ke liye phir taiyaar.

Left mein zameen se upar stratosphere label wali ek shaded band tak ek column. Step 1: ek CCl2F2 molecule zameen par hai. Step 2: woh stratosphere mein chadh gaya hai, ek lehardaar UV arrow us par padta hai aur ek chlorine atom, Cl·, chhoot jaata hai; right mein ek cycle ke upar bhi ek Cl· node dikhta hai. Step 3: + O3 label wala ek arrow cycle ki right side se ghoomkar ClO· node tak jaata hai, aur uske neeche note O2 nikla hai. Step 4: + O label wala ek arrow left side se wapas Cl· tak jaata hai, loop band karta hai, aur ek doosre note par likha hai Cl· wapas aaya. Dono equations figure ke neeche likhi hain.

Chlorine cycle

\begin{aligned} C l \cdot + O_{3} \\ \overset{}{\to} C l O \cdot + O_{2} \\ C l O \cdot + O \\ \overset{}{\to} C l \cdot + O_{2} \end{aligned}

6.8.6 p,p'-Dichlorodiphenyltrichloroethane (DDT)

DDT, $(C l C_{6} H_{4})_{2} C H - C C l_{3}$ , pehla chlorinated organic insecticide tha jo bahut bade paimane par use hua. 1940s se ise gharon mein aur kheton aur daldalon par malaria failane wale mosquitoes aur typhus failane wali joonon ke khilaaf spray kiya gaya. 1953 mein shuru hua India ka National Malaria Control Programme indoor DDT spraying par tika tha, aur 1960s ke beech tak malaria cases saal ke karodon se ghatkar lagbhag ek lakh reh gaye.

Timeline

DDT ka utthaan aur patan

1874
Pehli baar bana
Othmar Zeidler laboratory mein DDT banate hain lekin iska koi use nahi dhoondh paate.
1939
Ek powerful insecticide
Switzerland mein Geigy mein Paul Müller paate hain ki yeh chhoote hi insects ko maar deta hai.
1948
Nobel Prize
Müller ko Physiology or Medicine ka Nobel Prize milta hai.
1962
Silent Spring
Rachel Carson ki kitaab birds aur wildlife ko hone wale nuksaan ka varnan karti hai.
1972
USA mein ban
Zyaadatar uses band; kai desh peeche-peeche chalte hain.
2001
Stockholm Convention
Duniya bhar mein DDT sirf beemari failane wale insects ko control karne tak seemit kar diya jaata hai.

DDT ki kamzori yeh hai ki yeh jaata hi nahi. Iska molecule chemical aur biological attack ka virodh karta hai, aur yeh water ke muqable fats aur oils mein kahin behtar dissolve hota hai. Jo jaanwar DDT leta hai woh na use jaldi tod sakta hai na urine mein bahar nikaal sakta hai, isliye DDT uske fatty tissue mein jama hota hai aur har khaane ke saath yeh store badhta hai. Ek predator apne khaaye har shikaar ka store le leta hai, isliye food chain ke har level par concentration badhta hai (Fig. 6.19). Sabse upar, machhli khaane wale birds ne itne patle shells wale ande diye ki woh bach nahi paaye. Bade paimane par spraying ke kuch saalon mein do aur problems saamne aayin: DDT machhliyon ke liye bahut zehreela nikla, aur kai insect populations is par resistant ho gayin.

4/4Top predators mein water ke level ka lagbhag ek million guna hota hai.

Fig. 6.19Illustrative numbers: har feeding level fat-soluble DDT ko aur concentrate karta hai.

Left se right paanch icons ki ek row: water, plankton, ek chhoti machhli, ek badi machhli aur ek heron (bagula), arrows se jude, aur har icon par dots stored DDT dikhate hain. Har ek ke neeche illustrative scale par water ke relative concentration likha hai. Step 1 water dikhata hai, ek dot aur times 1, aur plankton, teen dots aur times 10 cubed. Step 2 chhoti machhli jodta hai, chhe dots aur times 10 to the fourth. Step 3 badi machhli jodta hai, gyarah dots aur times 10 to the fifth. Step 4 ek heron jodta hai, do taangon par khada aur lambi gardan wala, solah dots aur times 10 to the sixth ke saath.

Quick check

3 mein se 1

Har compound ko uske baare mein ek fact se match karo.

Left mein koi item tap karo, phir right mein uska match.

Answer dekho

Answer

$C H C l_{3}$ : air aur light mein phosgene ban jaata hai
$C H I_{3}$ : iodine chhodkar antiseptic ki tarah kaam karta hai
$C C l_{2} F_{2}$ : refrigerant jo ozone layer ko nuksaan pahunchata hai
DDT : body fat mein store hota hai
$C H_{2} C l_{2}$ : paint hatane wala solvent

Is section mein har compound ke liye bataye gaye yeh main uses aur khatre hain.

Recap

Summary aur key points

Haloalkanes mein X $s p^{3}$ carbon par hota hai aur haloarenes mein aromatic $s p^{2}$ carbon par; halides ko X atoms ki ginti se, aur alkyl (1°, 2°, 3°), allylic, benzylic, vinylic ya aryl ke roop mein sort kiya jaata hai (Section 6.1).
IUPAC names halogens ko prefixes maante hain; common names alkyl + halide, o/m/p, aur dihalides ke liye gem/vic use karte hain (Section 6.2).
C–X bond polar hai (δ+ carbon) aur C–F se C–I tak lamba aur weak hota jaata hai (Section 6.3).
Haloalkanes alcohols (HX, PX₃, PCl₅, SOCl₂) se, alkanes (free radicals, mixtures) se, alkenes (HX, X₂) se aur halogen exchange (Finkelstein, Swarts) se bante hain (Section 6.4).
Haloarenes Lewis acid ke saath ring halogenation se, ya diazonium salts (Sandmeyer; iodides ke liye KI) se bante hain (Section 6.5).
Halides apne parent alkanes se zyada par ubalte hain; b.p. F se I tak badhta hai aur branching se ghatta hai; yeh water mein mushkil se dissolve hote hain, aur bromides, iodides aur polychlorides water se zyada dense hain (Section 6.6).
SN2: ek step, rate $= k [R X] [N u^{-}]$ , back-side attack aur inversion, methyl aur 1° halides ke liye sabse tez (SN2 mechanism).
SN1: planar carbocation tak slow ionisation, rate $= k [R X]$ , racemisation, 3°, allylic aur benzylic halides ke liye sabse tez (SN1 mechanism).
Chaar alag groups wala carbon stereocentre hai; chiral molecules optically active hote hain, enantiomers light ko barabar lekin ulti directions mein ghumate hain, aur racemic mixtures koi rotation nahi dikhate (Chirality aur enantiomers).
Alcoholic KOH β-elimination deta hai, jismein zyada substituted alkene major product hota hai (Zaitsev) (Elimination reactions).
Grignard reagents RMgX (dry ether) ka carbon δ− hota hai aur water unhe khatam kar deta hai; sodium halides ko jodta hai (Wurtz, Wurtz–Fittig, Fittig) (Metals ke saath reaction).
Haloarenes nucleophiles ka virodh karte hain jab tak o/p nitro groups anionic intermediate ko stable na karein; electrophilic substitution mein halogens deactivating hain lekin o/p-directing (Section 6.7.2).
Dichloromethane, chloroform, iodoform, carbon tetrachloride, freons aur DDT useful hain lekin health ko nuksaan pahuncha sakte hain, ozone ghata sakte hain ya food chains mein jama ho sakte hain (Section 6.8).

Flash cards · 9

Yaad rakhne wali named reactions

1 / 9

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Hamare practice questions ncert.ai ke liye likhe gaye hain aur NCERT exercises ko follow karte hain. Apni textbook ke question se match karne wala question dhoondo; uska answer uske saath hai.

Tumhari NCERT textbook mein	Yahan practice question
NCERT Intext Question 6.1	Practice: halides ke naam · Q1
NCERT Intext Question 6.2	Practice: halides banana · Q1
NCERT Intext Question 6.3	Practice: halides banana · Q2
NCERT Intext Question 6.4	Practice: halides banana · Q3
NCERT Intext Question 6.5	Practice: halides banana · Q4
NCERT Intext Questions 6.7–6.8	Practice: haloalkanes ki reactions · Q1
NCERT Intext Question 6.9	Practice: haloalkanes ki reactions · Q2
NCERT Exercises Q6.1	Exercises · Q1
NCERT Exercises Q6.2	Exercises · Q2
NCERT Exercises Q6.3	Exercises · Q3
NCERT Exercises Q6.4	Exercises · Q4
NCERT Exercises Q6.5	Exercises · Q5
NCERT Exercises Q6.6	Exercises · Q6
NCERT Exercises Q6.7	Exercises · Q7
NCERT Exercises Q6.8	Exercises · Q8
NCERT Exercises Q6.9	Exercises · Q9
NCERT Exercises Q6.10	Exercises · Q10
NCERT Exercises Q6.11	Exercises · Q11
NCERT Exercises Q6.12	Exercises · Q12
NCERT Exercises Q6.13	Exercises · Q13
NCERT Exercises Q6.14	Exercises · Q14
NCERT Exercises Q6.15	Exercises · Q15
NCERT Exercises Q6.16	Exercises · Q16
NCERT Exercises Q6.17	Exercises · Q17
NCERT Exercises Q6.18	Exercises · Q18
NCERT Exercises Q6.19	Exercises · Q19
NCERT Exercises Q6.20	Exercises · Q20
NCERT Exercises Q6.21	Exercises · Q21
NCERT Exercises Q6.22	Exercises · Q22

Quick check: MCQs

6.1.3 sp² C—X bond wale compounds3 questions
6.2 Nomenclature3 questions
6.3 C—X bond ka nature3 questions
6.4.3 Halogen Exchange4 questions
6.5 Haloarenes banana3 questions
6.6 Physical Properties4 questions
SN1 mechanism4 questions
Retention, inversion aur racemisation4 questions
Metals ke saath reaction4 questions
Metals ke saath reaction4 questions
6.8.6 p,p'-Dichlorodiphenyltrichloroethane (DDT)3 questions

Glossary · 15

Key terms (English + Hindi)

ambident nucleophile: Aisa nucleophile jismein attack kar sakne wale do alag atoms hon, jaise cyanide (C ya N) aur nitrite (O ya N).Chapter mein pehli baar yahan aaya →

carbocationकार्बधनायनkaarbdhanaayan: Ek planar ion jiska positively charged $s p^{2}$ carbon sirf chhe valence electrons rakhta hai.Chapter mein pehli baar yahan aaya →
chiralकिरलkiral: Apni mirror image par superimpose na ho sakne wala, jaise left haath; jo superimpose ho sake woh achiral hai.Chapter mein pehli baar yahan aaya →

enantiomer: Stereoisomers ke us pair ka ek member jo ek doosre ki non-superimposable mirror images hain.Chapter mein pehli baar yahan aaya →

Grignard reagent: Alkyl- ya arylmagnesium halide, $R M g X$ , jo dry ether mein halide aur magnesium se banta hai; iska carbon strongly basic hota hai.Chapter mein pehli baar yahan aaya →

haloalkaneहैलोऐल्केनhailoalkane: Aisa compound jismein halogen atom kisi alkyl group ke $s p^{3}$ carbon se juda ho, $R - X$ .Chapter mein pehli baar yahan aaya →
haloareneहैलोऐरीनhailoareen: Aisa compound jismein halogen atom seedha aromatic ring ke $s p^{2}$ carbon se juda ho, $A r - X$ .Chapter mein pehli baar yahan aaya →

leaving group: Woh atom ya group jo substitution ya elimination mein bonding pair lekar nikal jaata hai; haloalkanes mein yeh halide ion hai.Chapter mein pehli baar yahan aaya →

nucleophileनाभिकस्नेहीnaabhikasnehi: Electron-rich species (anion ya lone pair wala molecule) jo electron-poor carbon par attack karke usse naya bond banati hai.Chapter mein pehli baar yahan aaya →

optical activityध्रुवण घूर्णकताdhruvan ghoornakta: Kisi substance ki plane-polarised light ke plane ko ghumane ki kshamta; clockwise (+) hai, anticlockwise (−).Chapter mein pehli baar yahan aaya →

racemic mixtureरेसिमिक मिश्रणresimik mishran: Do enantiomers ka 50 : 50 mixture; yeh koi optical rotation nahi dikhata aur (±) prefix ke saath likha jaata hai.Chapter mein pehli baar yahan aaya →

SN1 reaction: Unimolecular nucleophilic substitution: carbocation tak slow ionisation, phir fast capture; rate $= k [R X]$ .
SN2 reaction: Bimolecular nucleophilic substitution: ek step, rate $= k [R X] [N u^{-}]$ , back-side attack aur configuration ka inversion.
stereocentre: Chaar alag groups se juda carbon atom; inmein se koi bhi do badalne par mirror-image arrangement banti hai.Chapter mein pehli baar yahan aaya →

β-eliminationविलोपनvilopan: β-carbon se hydrogen aur α-carbon se halogen ka nikalna, jisse C=C double bond banta hai.Chapter mein pehli baar yahan aaya →

6.1 Classification

6.1.1 Halogen atoms ki ginti ke aadhaar par

6.1.2 sp³ C—X bond wale compounds

6.1.3 sp² C—X bond wale compounds

6.2 Nomenclature

6.3 C—X bond ka nature

6.4 Haloalkanes banane ke tareeke

6.4.1 Alcohols se

6.4.2 Hydrocarbons se

6.4.3 Halogen Exchange

6.5 Haloarenes banana

6.6 Physical Properties

6.7 Chemical Reactions

6.7.1 Haloalkanes ki reactions

Nucleophilic substitution

SN2 mechanism

SN1 mechanism

Optical activity

Chirality aur enantiomers

Retention, inversion aur racemisation

Elimination reactions

Metals ke saath reaction

6.7.2 Haloarenes ki reactions

Nucleophilic substitution

Electrophilic substitution

Metals ke saath reaction

6.8 Polyhalogen Compounds

6.8.1 Dichloromethane (Methylene chloride)

6.8.2 Trichloromethane (Chloroform)

6.8.3 Triiodomethane (Iodoform)

6.8.4 Tetrachloromethane (Carbon tetrachloride)

6.8.5 Freons

6.8.6 p,p'-Dichlorodiphenyltrichloroethane (DDT)

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