Chemistry Textbook Part II PDF for Class XII

CHEMISTRY Part II Textbook for Class XII 12 f}Hkkf"kd (Bilingual) BIHAR STATE TEXTBOOK PUBLISHING CORPORATION LTD., BUDH MARG, PATNA-1 fcgkj LVsV VsDLVcqd ifCyf'kax dkWjiksjs'ku fyfeVsM] cq¼ ekxZ] iVuk&1 Free Distribution- 2024-25 vij eq[; lfpo] f'k{kk foHkkx] fcgkj ds ekxZn'kZu esaA funs'kd (ekè;fed f'k{kk)] f'k{kk foHkkx] fcgkj ljdkj }kjk Lohd`rA jk"Vªh; 'kSf{kd vuqla/kku vkSj izf'k{k.k ifj"kn~] ubZ fnYyh ds lkStU; ls lEiw.kZ fcgkj jkT; ds fufeÙkA jk"Vªh; 'kSf{kd vuqla/kku vkSj izf'k{k.k ifj"kn~] ubZ fnYyh la'kksf/r laLdj.k flracj 2022] Hkknzin 1944 ekpZ 2024 pS=k 1946 izFke laLdj.k % 2024 (f}Hkkf"kd) fu%'kqYd forj.k fcgkj LVsV VsDLVcqd ifCyf'kax dkWjiksjs'ku fyfeVsM] ikB~;&iqLrd Hkou] cq¼ekxZ] iVuk&800001 }kjk izdkf'kr rFkk ------------------------------------------------- }kjk 80 th-,l-,e- VsDLV isij (------------------------- ----------------- ) rFkk 220 th-,l-,e- vkVZ cksMZ (---------------------------------------------fey) vkoj.k isij ij dqy ----------------------izfr;k¡ 21 ´ 27-5 lss-eh- lkbt esa eqfnzrA fu%'kqYd forj.k&2024&25 ikB~;iqLrd fodkl lfefr vè;{k] foKku vkSj xf.kr ikB~;iqLrd lykgdkj lfefr t;ar fo".kq ukyhZdj] izksi+sQlj] vè;{k] lykgdkj lfefrA varj&fo'ofo|ky; osaQnz] [kxksyfoKku vkSj [kxksy HkkSfrdh] (IUCAA)] iq.ks fo'ofo|ky; ifjlj] iq.ksA eq[; lykgdkj ch-,y- [kaMsyoky] izksI+ksQlj] funs'kd] fn'kk baLVhV~;wV vkWiQ eSustesaV rFkk VSDuksyksth] jk;iqj] NÙkhlxk] ,lksfl,V izksI+kQs lj] fo'kq¼ ,oa vuqiz;qDr jlk;u foHkkx] e-n-l- fo'ofo|ky;] vtesjA js.kq ikjk'kj] izoDrk] galjkt egkfo|ky;] fnYyh fo'ofo|ky;] fnYyhA lqjsUnz vjksM+k] ofj"B izoDrk] jlk;u foHkkx] jktdh; egkfo|ky;] vtesjA viii CONTENTS iii v FOREWORD ix RATIONALISATION OF CONTENT IN THE TEXTBOOK PREFACE 163 Unit 6 Haloalkanes and Haloarenes 164 6.1 Classification 165 6.2 Nomenclature 167 6.3 Nature of C–X Bond 168 6.4 Methods of Preparation of Haloalkanes 170 6.5 Preparation of Haloarenes 172 6.6 Physical Properties 174 6.7 Chemical Reactions 191 6.8 Polyhalogen Compounds 198 Unit 7 Alcohols, Phenols and Ethers 199 7.1 Classification 201 7.2 Nomenclature 204 7.3 Structures of Functional Groups 205 7.4 Alcohols and Phenols 220 7.5 Some Commercially Important Alcohols 221 7.6 Ethers 233 Unit 8 Aldehydes, Ketones and Carboxylic Acids 234 8.1 Nomenclature and Structure of Carbonyl Group 8.2 Preparation of Aldehydes and Ketones 237 8.3 Physical Properties 241 8.4 Chemical Reactions 242 8.5 Uses of Aldehydes and Ketones 250 8.6 Nomenclature and Structure of Carboxyl Group 250 8.7 Methods of Preparation of Carboxylic Acids 252 8.8 Physical Properties 255 xiii fo"k;&lwph vkeq[k iii izLrkouk v ikB~;iqLrdksa esa ikB~; lkexzh dk iqul±;kstu ix ,dd 6 gSyks,sYosQu rFkk gSyks,sjhu 163 6.1 oxhZdj.k 164 6.2 ukei¼fr 165 6.3 C-X vkcaèk dh izÑfr 167 6.4 ,sfYdy gSykbMksa osQ fojpu dh fofèk;k¡ 168 6.5 gSyks,jhuksa dk fojpu 170 6.6 HkkSfrd xq.k 172 6.7 jklk;fud vfHkfØ;k,¡ 174 6.8 ikWfygSykstu ;kSfxd 191 ,dd 7 ,sYdksgkWy] I k+ QhukWy ,oa bZFkj 198 7.1 oxhZdj.k 199 7.2 ukei¼fr 201 7.3 izdk;kZRed lewgksa dh lajpuk,¡ 204 7.4 ,sYdksgkWy vkSj I+kQhukWyksa dk fojpu 205 7.5 vkS|ksfxd egRo osQ oqQN ,sYdksgkWy 220 7.6 bZFkj 221 ,dd 8 ,sfYMgkbM] dhVksu ,oa dkcksZfDlfyd vEy 233 8.1 dkcksZfuy ;kSfxdksa dk ukedj.k ,oa lajpuk 234 8.2 ,sfYMgkbMksa ,oa dhVksuksa dk fojpu 237 8.3 HkkSfrd xq.kèkeZ 241 8.4 jklk;fud vfHkfØ;k,¡ 242 8.5 ,sfYMgkbMksa ,oa dhVksuksa osQ mi;ksx 250 8.6 dkcksZfDlfyd lewg dh ukei¼fr o lajpuk 250 8.7 dkcksZfDlfyd vEy cukus dh fofèk;k¡ 252 8.8 HkkSfrd xq.k 255 8.9 Chemical Reactions 255 8.10 Uses of Carboxylic Acids 260 Unit 9 Amines 266 9.1 Structure of Amines 266 9.2 Classification 267 9.3 Nomenclature 267 9.4 Preparation of Amines 269 9.5 Physical Properties 272 9.6 Chemical Reactions 273 9.7 Method of Preparation of Diazonium Salts 282 9.8 Physical Properties 9.9 Chemical Reactions 282 9.10 Importance of Diazonium Salts in Synthesis of 282 Aromatic Compounds 284 Unit 10 Biomolecules 288 10.1 Carbohydrates 288 10.2 Proteins 297 10.3 Enzymes 302 10.4 Vitamins 302 10.5 Nucleic Acids 304 10.6 Hormones 307 Answers to Some Questions in Exercises 310 CONTENTS OF CHEMISTRY PART I UNIT 1 SOLUTIONS 1 UNIT 2 ELECTROCHEMISTRY 31 UNIT 3 CHEMICAL KINETICS 61 UNIT 4 THE d-AND f-BLOCK ELEMENTS 89 UNIT 5 COORDINATION COMPOUNDS 118 APPENDICES 141 ANSWERS TO SOME QUESTIONS IN EXERCISES 154 xiv 8.9 jklk;fud vfHkfØ;k,¡ 255 8.10 dkcksZfDlfyd vEyksa osQ mi;ksx 260 ,dd 9 ,sehu 266 9.1 ,sehuksa dh lajpuk 266 9.2 oxhZdj.k 267 9.3 ukei¼fr 267 9.4 ,sehuksa dk fojpu 269 9.5 HkkSfrd xq.kèkeZ 272 9.6 jklk;fud vfHkfØ;k,¡ 273 9.7 Mkb,tksfu;e yo.kksa osQ fojpu dh fofèk 282 9.8 HkkSfrd xq.k 282 9.9 jklk;fud vfHkfØ;k,¡ 282 9.10 ,sjkseSfVd ;kSfxdksa osQ la'ys"k.k esa Mkb,s”kksyo.kksa dk egRo 284 ,dd 10 tSo&v.kq 288 10.1 dkcksgZ kbMªsV 288 10.2 izkVs hu 297 10.3 ,Utkbe 302 10.4 foVkfeu 302 10.5 U;wDyhd vEy 304 10.6 gkeksuZ 307 oqQN vH;klkFkZ iz'uksa osQ mÙkj 310 izFke Hkkx dh fo"k;&lwph 1 foy;u 1 2 oS|qrjlk;u 31 3 jklk;fud cyxfrdh 63 4 d- ,oa f- CykWd osQ rRo 91 5 milgla;kstu ;kSfxd 120 xii Unit Objectives 6 Haloalkanes and Haloar enes After studying this Unit, you will be able to name haloalkanes and haloarenes Haloarenes according to the IUPAC system of nomenclature from their given structures; Halogenated compounds persist in the environment due to their describe the reactions involved in resistance to breakdown by soil bacteria. the preparation of haloalkanes and haloarenes and understand various reactions that they The replacement of hydrogen atom(s) in a n aliphatic undergo; or aromatic hydrocarbon by halogen atom(s) results correlate the structures of in the formation of alkyl halide (haloalkane) and aryl haloalkanes and haloarenes with halide (haloarene), respectively. Haloalkanes contain various types of reactions; halogen atom(s) attached to the sp3 hybridised carbon use stereochemistry as a tool for atom of an alkyl group whereas haloarenes contain understanding the reaction halogen atom(s) attached to sp2 hybridised carbon mechanism; atom(s) of an aryl group. Many halogen containing appreciate the applications of organo-metallic compounds; organic compounds occur in nature and some of these are clinically useful. These classes of compounds highlight the environmental effects of polyhalogen compounds. find wide applications in industry as well as in day- to-day life. They are used as solvents for relatively non-polar compounds and as starting materials for the synthesis of wide range of organic compounds. Chlorine containing antibiotic, chloramphenicol, produced by microorganisms is very effective for the treatment of typhoid fever. Our body pr oduces iodine containing hormone, thyroxine, the deficiency of which causes a disease called goiter. Synthetic halogen compounds, viz. chloroquine is used for the treatment of malaria; halothane is used as an anaesthetic during surgery. Certain fully fluorinated compounds are being considered as potential blood substitutes in surgery. In this Unit, you will study the important methods of preparation, physical and chemical properties and uses of organohalogen compounds. ,dd mís'; bl ,dd osQ vè;;u osQ i'pkr~ vki & 6 gSyks,sYosQu rFkk IUPAC iz.kkyh dh ukei¼fr ls gSyks,sYosQuksa rFkk gSyks,sjhuksa dh nh xbZ lajpuk dk ukedj.k gSyks,sjhu dj losQa xs_ gSyks,Ys osQuksa rFkk gSyks,js huksa osQ fojpu esa iz;Dq r gksus okyh vfHkfØ;kvksa dk o.kZu dj losQaxs rFkk buosQ }kjk nh tkus okyh fofHkUu vfHkfØ;kvksa gSykstu;qDr ;kSfxd i;kZoj.k esa yacs le; rd cus jgrs gSa D;ksafd ;g e`nk osQ dks le> losaQxs_ thok.kqvksa }kjk Hkatu osQ izfr izfrjks/h gksrs gSaA fofHkUu izdkj dh vfHkfØ;kvksa rFkk gSyks,Ys osQuksa ,oa gSyks,js huksa dh lajpukvksa dks lglacfa /r dj ,sfyiSQfVd vFkok ,sjkseSfVd gkbMªksdkcZu osQ gkbMªkstu ijek.kq (vFkok losQa xs_ ijek.kqvksa) dk gSykstu ijek.kq (vFkok ijek.kqvksa) }kjk izfrLFkkiu gksus ls Øe'k% ,sfYdy gSykbM (gSyks,Ys osQu) rFkk ,sfjy gSykbM (gSyks,js hu) vfHkfØ;k dh fØ;kfof/ dks le>us esa f=kfoejlk;u dk mi;ksx dj losaQxs_ curs gSaA gSyks,sYosQuksa esa gSykstu ijek.kq ,sfYdy lewg osQ sp3 ladfjr dkcZu ijek.kq (ijek.kqvks)a ls tqMk+ jgrk gS tcfd gSyks,js huksa esa gSykstu dkcZ/kfRod ;kSfxdksa osQ vuqiz;ksxksa dk egRo ijek.kq ,sfjy lewg osQ sp2 ladfjr dkcZu ijek.kq (ijek.kqvksa) ls le> losQa xs_ tqM+k jgrk gSA cgqr ls gSykstu;qDr dkcZfud ;kSfxd izÑfr esa feyrs ikWfygSykstu ;kSfxdksa osQ i;kZoj.k ij izHkkoksa dks gSa rFkk buesa ls oqQN fpfdRldh; :i ls mi;ksxh gksrs gSaA bl oxZ vfrnhIr dj losaQxsA osQ ;kSfxdksa osQ mi;ksxksa dk foLrkj m|ksxksa esa rFkk nSfud thou esa cgqr cM+k gSA budk mi;ksx vis{kkÑr vèkzqoh; ;kSfxdksa osQ fy, foyk;d osQ :i esa rFkk vusd izdkj osQ dkcZfud ;kSfxdksa osQ la'ys"k.k osQ fy, izkjafHkd inkFkZ osQ :i esa gksrk gSA lw{ethfo;ksa }kjk mRikfnr DyksjSEisQfudkWy] tks fd Dyksjhu;qDr izfrtSfod (,sfUVck;ksfVd) gS] vka=kToj (Vkbi+WQkbM) osQ bykt esa vR;fèkd izHkkoh gksrh gSA gekjs 'kjhj esa vk;ksMhu;qDr gkeksZu] FkkbjkWfDlu mRiUu gksrk gS ftldh deh ls xyxaM (?ksa?kk) uked jksx gks tkrk gSA la'ysf"kr gSykstu ;kSfxd tSls] DyksjksDohu dk mi;ksx eysfj;k osQ mipkj esa gksrk gSA gSyksFksu dk mi;ksx 'kY; fpfdRlk esa fu'psrd osQ :i esa gksrk gSA oqQN iw.kZr% ÝyqvksjhuhÑr ;kSfxdksa dks 'kY; fpfdRlk esa izHkkoh jDr izfrLFkkih osQ :i esa ns[kk tk jgk gSA bl ,dd esa vki dkcZgSykstu ;kSSfxdksa osQ fojpu dh izeq[k fofèk;ksa] HkkSfrd ,oa jklk;fud xq.kksa rFkk mi;ksxksa dk vè;;u djsaxsA Free Distribution, 2024-25 6.1 Classification Haloalkanes and haloarenes may be classified as follows: 6.1.1 On the These may be classified as mono, di, or polyhalogen (tri-,tetra-, etc.) Basis of compounds depending on whether they contain one, two or more halogen Number of atoms in their structures. For example, Halogen Atoms Monohalocompounds may further be classified according to the hybridisation of the carbon atom to which the halogen is bonded, as discussed below. 6.1.2 Compounds This class includes Containing (a) Alkyl halides or haloalkanes (R—X) sp3 C—X Bond (X= F, In alkyl halides, the halogen atom is bonded to an alkyl group (R). Cl, Br, I) They form a homologous series represented by CnH2n+1X. They are further classified as primary, secondary or tertiary according to the nature of carbon to which halogen is attached.If halogen is attached to a primary carbon atom in an alkyl halide, the alkyl halide is called primary alkyl halide or 1 alkyl halide. Similarly, if halogen is attached to secondary or tertiary carbon atom, the alkyl halide is called secondary alkyl halide (2 ) and tertiary (3 ) alkyl halide, respectively. (b) Allylic halides These are the compounds in which the halogen atom is bonded to an sp3-hybridised carbon atom adjacent to carbon-carbon double bond (C=C) i.e. to an allylic carbon. Allylic carbon Allylic carbon (c) Benzylic halides These are the compounds in which the halogen atom is bonded to an sp3-hybridised carbon atom attached to an aromatic ring. Chemistry 164 fu%'kqYd forj.k] 2024&25 6-1 oxhZdj.k gSyks,sYosQuksa rFkk gSyks,sjhuksa dks fuEu izdkj ls oxhZÑr fd;k tk ldrk gSμ lajpuk esa mifLFkr ,d] nks vFkok vfèkd gSykstu ijek.kqvksa dh la[;k osQ vkèkkj 6-1-1 gSykstu ijek.kqvksa ij bUgsa eksuks] Mkb vFkok ikWfygSykstu (Vªkb& VsVªk& vkfn) esa oxhZÑr fd;k tk dh la[;k osQ ldrk gSA mnkgj.kkFkZμ vk/kj ij eksuksgSyks;kSfxdksa dks] ml dkcZu ijek.kq osQ ladj.k osQ vkèkkj ij iqu% oxhZÑr fd;k tk ldrk gSs ftlls gSykstu ijek.kq vkcafèkr gksrk gSA tSlk fd uhps of.kZr fd;k x;k gSA bl oxZ esa lfEefyr gS— a 6-1-2 sp3 C–X vkcaèk (d) ,sfYdy gSykbM vFkok gSyks,sYosQu (R–X) ,sfYdy gSykbMksa esa gSykstu ijek.kq ,sfYdy lewg (R) ls vkcafèkr jgrk gSA ;s ,d ;qDr ;kSfxd ltkrh; Js.kh cukrs gSa ftls CnH2n+1X ls iznf'kZr djrs gSAa bUgsa ml dkcZu ijek.kq (X = F, Cl, Br, I) dh izÑfr osQ vkèkkj ij iqu% izkFkfed] f}rh;d vFkok r`rh;d esa oxhZÑr fd;k x;k gSA ftlls gSykstu ijek.kq vkcafèkr gksrk gSA ;fn ,sfYdy gSykbM esa gSykstu izkFkfed dkcZu ls tqM+k gks rks mls izkFkfed ,sfYdy gSykbM vFkok 1 ,sfYdy gSykbM dgrs gSaA blh izdkj ls ;fn gSykstu f}rh;d ;k r`rh;d dkcZu ijek.kq ls tqM+k gks rks mls Øe'k% f}rh;d (vFkok 2 ) vkSj r`rh;d (vFkok 3 ) ,sfYdy gSykbM dgrs gSaA ([k) ,sfyfyd gSykbM ;g os ;kSfxd gksrs gSa ftuesa gSykstu ijek.kq dkcZuμdkcZu f}d vkcaèk (C=C) osQ lehiorhZ sp3 ladfjr dkcZu ijek.kq ls vkcafèkr jgrk gS vFkkZr~ ,d ,sfyfyd dkcZu ls vkcafaèkr gksrk gSA (x) csfUTkfyd gSykbM bl izdkj osQ ;kSfxdksa esa gSykstu ijek.kq ,sjkseSfVd oy; ls tqM+s sp3 ladfjr dkcZu ijek.kq ls vkcafèkr jgrk gSA 164 jlk;u foKku Free Distribution, 2024-25 6.1.3 Compounds This class includes: Containing (a) Vinylic halides sp2 C—X Bond These are the compounds in which the halogen atom is bonded to a sp2-hybridised carbon atom of a carbon-carbon double bond (C = C). (b) Aryl halides These are the compounds in which the halogen atom is directly bonded to the sp2-hybridised carbon atom of an aromatic ring. 6.2 Nomenclature Having learnt the classification of halogenated compounds, let us now learn how these are named. The common names of alkyl halides are derived by naming the alkyl group followed by the name of halide. In the IUPAC system of nomenclature, alkyl halides are named as halosubstituted hydrocarbons. For mono halogen substituted derivatives of benzene, common and IUPAC names are the same. For dihalogen derivatives, the prefixes o-, m-, p- are used in common system but in IUPAC system, as you have learnt in Class XI, the numerals 1,2; 1,3 and 1,4 are used. The dihaloalkanes having the same type of halogen atoms are named as alkylidene or alkylene dihalides. The dihalo-compounds having both the halogen atoms are further classified as geminal halides or gem-dihalides when both the halogen atoms are present on the same carbon atom of the Haloalkanes and Haloarenes 165 fu%'kqYd forj.k] 2024&25 6-1-3 sp2 C–X bl oxZ esa 'kkfey gSaμ vkcaèk;qDr (d) okbfufyd gSykbM ;kSfxd bl izdkj osQ ;kSfxdksa esa gSykstu ijek.kq dkcZu&dkcZu f}o~Q vkcaèk (C = C) osQ sp2 ladfjr dkcZu ijek.kq ls lh/s tqM+k jgrk gSA ([k) ,sfjy gSykbM bl izdkj osQ ;kSfxdksa esa gSykstu ijek.kq ,d ,sjkseSfVd oy; osQ sp2 ladfjr dkcZu ijek.kq ls lh/s tqM+k jgrk gSA 6-2 ukei)fr gSykstu ;kSfxdksa dk oxhZdj.k lh[kus osQ i'pkr~ vkb, vc ge lh[ksas fd bUgsa uke oSQls fn;k tkrk gSA ,sfYdy gSykbMksa osQ lkekU; uke dks O;qfRir djus osQ fy, ,sfYdy lewg dk uke fy[kus osQ i'pkr gSykbM dk uke fy[kk tkrk gS A ukedj.k dh IUPAC i¼fr es a ,s f Ydy gS y kbM dk ukedj.k gSyksizfrLFkkih gkbMªksdkcZu osQ :i esa fd;k tkrk gaSA ,d gSykstu okys csUthu osQ O;qRiUuksa osQ lkekU; vkSj IUPAC uke ,d gh gksrs gSaA MkbgSykstu O;qRiUuksa osQ fy, lkekU; iz.kkyh esa o-, m-, rFkk p- iwoZyXu dk mi;ksx djrs gSaA tcfd tSlk vki d{kk&11 osQ ,dd&8 esa tku pqosQ gSaA IUPAC i¼fr esa blosQ fy, 1] 2_ 1] 3 rFkk 1] 4 la[;kvksa dk mi;ksx djrs gSaA leku gSykstu ijek.kq;qDr MkbgSyks,sYosQuksa dks ,sfYdfyMhu ;k ,sfYdyhu MkbgSykbM dgrs gSaA ;fn leku gSykstu ijek.kq;qDr MkbgSyks ;kSfxd esa nksuksa gSykstu ijek.kq Ük`a[kyk osQ ,d gh dkcZu ijek.kq ij mifLFkr gksa rks bls tse MkbgSykbM 165 gSyks,sYosQu rFkk gSyks,sjhu Free Distribution, 2024-25 chain and vicinal halides or vic-dihalides when halogen atoms are present on adjacent carbon atoms. In common name system, gem-dihalides are named as alkylidene halides and vic-dihalides are named as alkylene dihalides. In IUPAC system, they are named as dihaloalkanes. Some common examples of halocompounds are mentioned in Table 6.1. Table 6.1: Common and IUPAC Names of some Halides Structure Common name IUPAC name CH3CH2CH(Cl)CH3 sec-Butyl chloride 2-Chlorobutane (CH3)3CCH2Br neo-Pentyl bromide 1-Bromo-2,2-dimethylpropane (CH3)3CBr tert-Butyl bromide 2-Bromo-2-methylpropane CH2 = CHCl Vinyl chloride Chloroethene CH2 = CHCH2Br Allyl bromide 3-Bromopropene o-Chlorotoluene 1-Chloro-2-methylbenzene or 2-Chlorotoluene Benzyl chloride Chlorophenylmethane CH2Cl2 Methylene chloride Dichloromethane CHCl3 Chloroform Trichloromethane CHBr3 Bromoform Tribromomethane CCl 4 Carbon tetrachloride Tetrachloromethane CH3CH2CH2F n-Propyl fluoride 1-Fluoropropane Chemistry 166 fu%'kqYd forj.k] 2024&25 ;k tSfeuy MkbgSykbM dgrs gSaA ;fn gSykstu ijek.kq Ük`a[kyk osQ nks fudVorhZ dkcZu ijek.kqvksa ij mifLFkr gksa rks mUgsa fofluy gSykbM dgk tkrk gSA lkekU; ukedj.ki¼fr esa tse&MkbgSykbM dks ,sfYdfyMhu gSykbM rFkk folμMkbgSykbM dks ,sfYdyhu MkbgSykbM osQ :i esa ukfer djrs gSaA IUPAC i¼fr esa bUgsa MkbgSyks,sYosQu osQ :i esa ukfer djrs gSaA oqQN izeq[k gSyks ;kSfxdksa osQ mnkgj.k lkj.kh 6-1 esa fn, x, gSaA lkj.kh 6-1µ oqQN gSykbMksa osQ lkekU; ,oa IUPAC uke izk:i lkekU; uke IUPAC uke CH3CH2CH(Cl)CH3 sec-C;wfVy DyksjkbM 2&DyksjksC;wVsu (CH3)CCH2Br neo-isfUVy czksekbM 1&czkes ks&2] 2&MkbesfFky izkis us (CH3)3CBr tert-C;wfVy czksekbM 2&czkseks&2&esfFky izksisu CH2=CHCl okbfuy DyksjkbM Dyksjks,Fkhu CH2=CHCH2Br ,sfyy czksekbM 3&czkseksizksihu o-DyksjksVkWywbZu 1&Dyksjks&2&esfFky csUthu ;k 2&DyksjksC;wVhu csfUty DyksjkbM Dyksjksi+sQfuy esFksu CH2Cl2 esfFkyhu DyksjkbM MkbDyksjksesFksu CHCl 3 DyksjksiQkWeZ VªkbDyksjksesFksu CHBr3 czkseksiQkWeZ VªkbczkseksesFksu CCl4 dkcZu VsVªkDyksjkbM VsVªkDyksjksesFksu CH3CH2CH2F - n izksfiy ÝyqvksjkbM 1&Ýyqvksjksizksisu 166 jlk;u foKku Free Distribution, 2024-25 Example 6.1 Draw the structures of all the eight structural isomers that have the molecular formula C5H11Br. Name each isomer according to IUPAC system and classify them as primary, secondary or tertiary bromide. Solution CH3CH2CH2CH2CH2Br 1-Bromopentane (1 ) o o CH3CH2CH2CH(Br)CH3 2-Bromopentane(2 ) o CH3CH2CH(Br)CH2CH3 3-Bromopentane (2 ) o (CH3)2CHCH2CH2Br 1-Bromo-3-methylbutane (1 ) o (CH3)2CHCHBrCH3 2-Bromo-3-methylbutane(2 ) o (CH3)2CBrCH2CH3 2-Bromo-2-methylbutane (3 ) o CH3CH2CH(CH3)CH2Br 1-Bromo-2-methylbutane(1 ) o (CH3)3CCH2Br 1-Bromo-2,2-dimethylpropane (1 ) Write IUPAC names of the following: Example 6.2 (i) 4-Bromopent-2-ene (ii) 3-Bromo-2-methylbut-1-ene Solution (iii) 4-Bromo-3-methylpent-2-ene (iv) 1-Bromo-2-methylbut-2-ene (v) 1-Bromobut-2-ene (vi) 3-Bromo-2-methylpropene Intext Question 6.1 Write structures of the following compounds: (i) 2-Chloro-3-methylpentane (ii) 1-Chloro-4-ethylcyclohexane (iii) 4-tert. Butyl-3-iodoheptane (iv) 1,4-Dibromobut-2-ene (v) 1-Bromo-4-sec. butyl-2-methylbenzene. 6.3 Nature of Halogen atoms are more electronegative than carbon, therefore, carbon-halogen bond of alkyl halide is polarised; the carbon atom bears C-X Bond a partial positive charge whereas the halogen atom bears a partial negative charge. As we go down the group in the periodic table, the size of halogen atom increases. Fluorine atom is the smallest and iodine atom is the Haloalkanes and Haloarenes 167 fu%'kqYd forj.k] 2024&25 mnkgj.k 6.1 C5H11Br v.kqlw=k okys vkB lajpukRed leko;fo;kas dh lajpuk,a cukb,A I U P A C i¼fr osQ vuqlkj lHkh leko;fo;ksa osQ uke nhft, rFkk mUgsa izkFkfed] f}rh;d ,oa Rk`rh;d czksekbMksa osQ :i esa oxhZÑr dhft,A gy CH3CH2CH2CH2CH2 Br 1&czkseksisUVsu (1 ) CH3CH2CH2CH(Br)CH3 2&czkseksisUVsu (2 ) CH3CH2CH2(Br)CH2CH3 3&czkseksisUVsu (2 ) (CH3)2CHCH2CH2Br 1&czkseks&3&esfFkyC;wVsu (CH3)2CHCH(Br)CH3 2&czkseks&3&esfFkyC;wVsu (CH3)2CBrCH2CH3 2&czkseks&2&esfFkyC;wVsu (3 ) CH3CH2CH(CH3)CH2Br 1&czkseks&2μesfFkyC;wVsu (1 ) (CH3)3CCH2Br 1-czkseks&2]2&MkbesfFkyizksisu (1 ) mnkgj.k 6.2 fuEufyf[kr osQ IUPAC uke fyf[k,μ gy (i) 4&czkseksisUV&2&bZu (ii) 3&czkseks&2&esfFkyC;wV&1&bZu (iii) 4&czkseks&3&esfFkyisUV&2&bZu (iv) 1&czkseks&2&esfFkyC;wV&2&bZu (v) 1&czkseksC;wV&2&bZu (vi) 3&czkseks&2&esfFky izksihu ikB~;fufgr iz'u 6.1 fuEufyf[kr ;kSfxdksa dh lajpuk,a fyf[k,— (i) 2&Dyksjks&3&esfFkyisUVsu (iv) 1] 4&MkbczkseksC;wV&2&bZu (ii) 1&Dyksjks&4&,fFkylkbDyksgsDlsu (v) 1&czkseks&4&f}rh;d&C;wfVy&2&esfFkycsU”khu (iii) 4&r`rh;d&C;wfVy&3&vk;MksgsIVsu 6-3 C-X vkca/k gSykstu ijek.kq] dkcZu ijek.kq dh rqyuk esa vfèkd fo|qr½.kkRed gksrk gS vr% ,sfYdy gSykbM dk dkcZu gSykstu vkcaèk èkqfz or gks tkrk gSA blls dkcZu ijek.kq dh izÑfr ij vkaf'kd èkukos'k rFkk gSykstu ijek.kq ij vkaf'kd ½.kkos'k vk tkrk gSA vkorZ lkj.kh esa oxZ esa Åij ls uhps dh vksj tkus ij gSykstu ijek.kq dk vkdkj c2 >1. Phosphorus tribromide and triiodide are usually generated in situ (produced in the reaction mixture) by the reaction of red phosphorus with bromine and iodine respectively. Chemistry 168 fu%'kqYd forj.k] 2024&25 ijek.kq lcls cM+s vkdkj dk gksrk gSA ifj.kker% dkcZu&gSykstu vkcaèk dh yackbZ C—F ls C—I rd c 2 > 1 gksrk + kQks+ jl VªkbczksekbM rFkk Vªkbvk;ksMkbM dks lkekU;r% yky I kQkLI gSA I kQkLI + kQks+ jl dh Øe'k% czksehu rFkk vk;ksMhu osQ lkFk vfHkfØ;k }kjk LoLFkkus ;kuh vfHkfØ;k feJ.k esa gh mRiUu fd;k tkrk gSA 168 jlk;u foKku Free Distribution, 2024-25 The preparation of alkyl chloride is carried out either by passing dry hydrogen chloride gas through a solution of alcohol or by heating a mixture of alcohol and concentrated aqueous halogen acid. The above methods are not applicable for the preparation of aryl halides because the carbon-oxygen bond in phenols has a partial double bond character and is difficult to break being stronger than a single bond. 6.4.2 From (I) From alkanes by free radical halogenation Hydrocarbons Free radical chlorination or bromination of alkanes gives a complex mixture of isomeric mono- and polyhaloalkanes, which is difficult to separate as pure compounds. Consequently, the yield of any single compound is low. (II) From alkenes (i) Addition of hydrogen halides : An alkene is converted to corresponding alkyl halide by reaction with hydrogen chloride, hydrogen bromide or hydrogen iodide. Propene yields two products, however only one predominates as per Markovnikov’s rule. (Unit 13, Class XI) (ii) Addition of halogens: In the laboratory, addition of bromine in CCl4 to an alkene resulting in discharge of reddish brown colour of bromine constitutes an important method for the detection of double bond in a molecule. The addition results in the synthesis of vic-dibromides, which are colourless (Unit 9, Class XI). 6.4.3 Halogen Alkyl iodides are often prepared by the reaction of alkyl chlorides/ Exchange bromides with NaI in dry acetone. This reaction is known asFinkelstein reaction. Haloalkanes and Haloarenes 169 fu%'kqYd forj.k] 2024&25 ,sfYdy DyksjkbM dk fojpu ,sYdksgkWy esa 'kq"d gkbMªkstu DyksjkbM xSl dks izokfgr djosQ vFkok lkanz tyh; gSykstu vEyksa osQ lkFk ,sYdksgkWy osQ feJ.k dks xje djosQ fd;k tk ldrk gSA ,sfjy gSykbM osQ fojpu osQ fy, mijksDr fofèk;k¡ mi;qDr ugha gSa_ D;ksafd I +kQhukWy esa dkcZu&vkWDlhtu vkcaèk esa vkaf'kd f}vkcaèk osQ xq.k gksus osQ dkj.k ;g ,dy vkcaèk ls vfèkd e”kcwr gksrk gS vr% bls ,dy vkcaèk dh rqyuk esa rksM+uk dfBu gksrk gSA 6-4-2 gkbMªksdkcZuksa ls (i) ,sYosQuksa ls eqDr ewyd gSykstuu }kjk ,sYosQuksa osQ eqDr ewyd Dyksjhuu vFkok czksehuu esa leko;oh eksuks rFkk ikWfygSyks,sYosQuksa dk tfVy feJ.k izkIr gksrk gS] ftls 'kq¼ ;kSfxdksa esa i`Fko~Q djuk dfBu gksrk gSA ifj.kker% fdlh Hkh ,d ;kSfxd dh yfCèk de gksrh gSA (,dd&9] d{kk&11) (ii) ,sYdhuksa ls (d) gkbMªkstu gSykbM osQ la;kstu ;k ;ksxt }kjk— gkbMªkstu DyksjkbM] gkbMªkstu czksekbM vFkok gkbMªkstu vk;ksMkbM ls vfHkfØ;k djus ij ,sYdhu laxr ,sfYdy gSykbM esa ifjofrZr gks tkrh gaSA izksihu nks izdkj osQ mRikn nsrh gS ijarq ekdkZsuhdkWiQ osQ fu;ekuqlkj ,d mRikn izeq[k gksrk gSA (,dd&9] d{kk&11) vYi eq[; ([k) gSykstu osQ la;kstu }kjk— CCl4 esa ?kqyh czksehu oQks ,sYdhu esa Mkyus ls czksehu dk yky jax foyqIr gks tkrk gSA ;g fdlh v.kq esa f}vkcaèk dh igpku djus dh ,d egRoiw.kZ iz;ksx'kkyk fofèk gSA bl la;kstu osQ ifj.kkeLo:i lafufèk MkbczksekbM (Vic-dibromide) dk la'ys"k.k gksrk gS tks fd jaxghu gksrk gSA (,dd&9] d{kk&11) 6-4-3 gSykstu fofue; ,sfYdy vk;ksMkbMksa dk fojpu izk;% ,sfYdy DyksjkbMksa@czksekbMksa dh 'kq"d ,slhVksu }kjk esa NaI osQ lkFk vfHkfØ;k ls gksrk gSA bl vfHkfØ;k dks fiaQosQYLVkbu vfHkfØ;k dgrs gSaA 169 gSyks,sYosQu rFkk gSyks,sjhu Free Distribution, 2024-25 NaCl or NaBr thus formed is precipitated in dry acetone. It facilitates the forward reaction according to Le Chatelier’s Principle. The synthesis of alkyl fluorides is best accomplished by heating an alkyl chloride/bromide in the presence of a metallic fluoride such as AgF, Hg2F2, CoF2 or SbF3. The reaction is termed as Swarts reaction. Identify all the possible monochloro structural isomers expected to be Example 6.3 formed on free radical monochlorination of (CH3)2CHCH2CH3. In the given molecule, there are four different types of hydrogen atoms. Solution Replacement of these hydrogen atoms will give the following (CH3)2CHCH2CH2Cl (CH3)2CHCH(Cl)CH3 (CH3)2C(Cl)CH2CH3 CH3CH(CH2Cl)CH2CH3 6.5 Preparation of (i) From hydrocarbons by electrophilic substitution Haloarenes Aryl chlorides and bromides can be easily prepared by electrophilic substitution of arenes with chlorine and bromine respectively in the presence of Lewis acid catalysts like iron or iron(III) chloride. The ortho and para isomers can be easily separated due to large difference in their melting points. Reactions with iodine are reversible in nature and require the presence of an oxidising agent (HNO3, HIO4) to oxidise the HI formed during iodination. Fluoro compounds are not prepared by this method due to high reactivity of fluorine. (ii) From amines by Sandmeyer’s reaction When a primary aromatic amine, dissolved or suspended in cold aqueous mineral acid, is treated with sodium nitrite, a diazonium salt is formed. Mixing the solution of freshly prepared diazonium salt with cuprous chloride or cuprous bromide results in the replacement of the diazonium gr oup by –Cl or –Br. Chemistry 170 fu%'kqYd forj.k] 2024&25 bl izdkj izkIr NaCl rFkk NaBr 'kq"d ,slhVksu esa vo{ksfir gks tkrs gSa rFkk ;g ys&'kkrSfy, osQ fu;ekuqlkj vxz vfHkfØ;k dks lqxe cuk nsrk gSA èkkfRod ÝyqvksjkbM tSls AgF, Hg 2F2, CoF2 vFkok SbF3 dh mifLFkfr esa ,sfYdy DyksjkbM@czksekbM dks xje djosQ miyCèk djuk] ,sfYdy ÝyqvksjkbMksa osQ la'ys"k.k dk loksZÙke rjhdk gSA bl vfHkfØ;k dks LokV~Zl vfHkfØ;k dgrs gaSA mnkgj.k 6.3 (CH3)2CHCH2CH3 osQ eqDr ewyd Dyksjhuu ls cuus okys lHkh laHkkfor eksuksDyksjks lajpukRed leko;oksa dks igpkfu,A gy fn, x, v.kq esa pkj fofHkUu izdkj osQ gkbMªkstu ijek.kq gSaA bu gkbMªkstu ijek.kqvksa osQ izfrLFkkiu ls fuEufyf[kr pkj eksuksDyksjks O;qRiUu izkIr gksaxsμ (CH3)2CHCH2CH2Cl, (CH3)2CHCH(Cl) CH3, (CH3)2C(Cl)CH2CH3, CH3CH(CH2Cl)CH2CH3 6-5 gSyks,jhuksa dk (i) gkbMªksdkcZuksa ls bysDVªkWujkxh izfrLFkkiu }kjk ,sfjy DyksjkbMksa rFkk czksekbMksa dk fojpu] vk;ju ;k vk;ju (III) DyksjkbM vFkok fojpu fdlh vU; ywbZl vEy mRiszjd dh mifLFkfr esa ,sjhuksa osQ Dyksjhu vFkok czksehu }kjk bysDVªkWujkxh izfrLFkkiu }kjk vklkuh ls fd;k tk ldrk gSA vkWFkksZ rFkk iSjk leko;oksa dks] muosQ xyukadksa esa vR;fèkd varj gksus osQ dkj.k lqxerkiwoZd i`Fko~Q fd;k tk ldrk gSA vk;ksMhu osQ lkFk vfHkfØ;k mRØe.kh; gksrh gS rFkk bl vfHkfØ;k esa mRiUu HI dks vkWDlhÑr djus osQ fy, vkWDlhdj.k deZd (HNO3, HIO3) dh vko';drk gksrh gSA Ýyqvksjhu dh vR;fèkd fØ;k'khyrk osQ dkj.k bl fofèk }kjk Ýyqvksjhu ;qDr ;kSfxdksa dk fojpu ugha fd;k tkrkA (ii) ,sehuksa ls lSUMek;j&vfHkfØ;k }kjk tc BaMs tyh; [kfut vEy esa ?kqyh vFkok fuyafcr fdlh izkFkfed ,sehu dks lksfM;e ukbVªkbV osQ lkFk vfHkÑr fd;k tkrk gS rks Mkb,s”kksfu;e yo.k curs gSa (,dd&9] d{kk 12)A rk”kk cus Mkb,s”kksfu;e yo.k rFkk D;wizl DyksjkbM vFkok D;wizl czksekbM osQ foy;u dks feykus ij Mkb”kksfu;e lewg – Cl vFkok & Br osQ }kjk izfrLFkkfir gks tkrk gSA 170 jlk;u foKku Free Distribution, 2024-25 Replacement of the diazonium group by iodine does not require the presence of cuprous halide and is done simply by shaking the diazonium salt with potassium iodide. Example 6.4 Write the products of the following reactions: Solution Intext Questions 6.2 Why is sulphuric acid not used during the reaction of alcohols with KI? 6.3 Write structures of different dihalogen derivatives of propane. 6.4 Among the isomeric alkanes of molecular formula C5H12, identify the one that on photochemical chlorination yields (i) A single monochloride. (ii) Three isomeric monochlorides. (iii) Four isomeric monochlorides. 6.5 Draw the structures of major monohalo products in each of the following reactions: Haloalkanes and Haloarenes 171 fu%'kqYd forj.k] 2024&25 vk;ksMhu }kjk Mkb,s”kksfu;e lewg osQ izfrLFkkiu osQ fy, D;wizl gSykbM dh mifLFkfr vko';d ugha gksrh rFkk bls lkekU;r% Mkb,s”kksfu;e yo.k rFkk iksVSf'k;e vk;ksMkbM osQ foy;u dks ,d lkFk fgykdj fd;k tkrk gSA mnkgj.k 6.4 fuEufyf[kr vfHkfØ;kvksa osQ mRikn fyf[k,μ gy ikB~;fufgr iz'u 6.2 ,sYdksgkWy rFkk KI dh vfHkfØ;k esa lYÝ;wfjd vEy dk mi;ksx D;ksa ugha djrs\ 6.3 izksisu osQ fofHkUu MkbgSykstu O;qRiUukas dh lajpuk fyf[k,A 6.4 C5H12 v.kqlw=k okys leko;oh ,sYosQuks esa ls mldks igpkfu, tks izdk'kjklk;fud Dyksjhuu ij nsrk gS— (i) osQoy ,d eksuksDyksjkbM] (ii) rhu leko;oh eksuksDyksjkbM] (iii) pkj leko;oh eksuksDyksjkbMA 6.5 fuEufyf[kr izR;sd vfHkfØ;k osQ eq[; eksuksgSyks mRikn dh ljapuk cukb,A 171 gSyks,sYosQu rFkk gSyks,sjhu Free Distribution, 2024-25 6.6 Physical Alkyl halides are colourless when pure. However, bromides and iodides develop colour when exposed to light. Many volatile halogen compounds Properties have sweet smell. Melting and boiling points Methyl chloride, methyl bromide, ethyl chloride and some chlorofluoromethanes are gases at room temperature. Higher members are liquids or solids. As we have already learnt, molecules of organic halogen compounds are generally polar. Due to greater polarity as well as higher molecular mass as compared to the parent hydrocarbon, the intermolecular forces of attraction (dipole-dipole and van der Waals) are stronger in the halogen derivatives. That is why the boiling points of chlorides, bromides and iodides are considerably higher than those of the hydrocarbons of comparable molecular mass. The attractions get stronger as the molecules get bigger in size and have more electrons. The pattern of variation of boiling points of different halides is depicted in Fig. 6.1. For the same alkyl group, the boiling points of alkyl halides decrease in the order: RI> RBr> RCl> RF. This is because with the increase in size and mass of halogen atom, the magnitude of van der Waal forces increases. Fig. 6.1: Comparison of boiling points of some alkyl halides The boiling points of isomeric haloalkanes decrease with increase in branching. For example, 2-bromo-2-methylpropane has the lowest boiling point among the three isomers. Chemistry 172 fu%'kqYd forj.k] 2024&25 6-6 HkkSfrd xq.k 'kq¼ voLFkk esa ,sfYdy gSykbM jaxghu ;kSfxd gksrs gSa ijarq czksekbM rFkk vk;ksMkbM] izdk'k osQ laioZQ esa vkus ij jaxhu gks tkrs gSaA vusoQ ok"i'khy gSykstu ;qDr ;kSfxd lqxaèke; gksrs gSaA xyukad ,oa DoFkukad esfFky DyksjkbM] esfFky czkes kbM] ,fFky DyksjkbM rFkk oqQN DyksjksÝyqvksjkseFs ksu dejs osQ rki ij xSl osQ :i esa gksrs gSa tcfd mPp lnL; nzo vFkok Bksl gksrs gSAa tSlk fd ge tkurs gS]a dkcZfud gSykstu ;kSfxdksa osQ v.kq lkekU;r% èkzoq h; gksrs gSaA mPp èkzoq rk ,oa tud gkbMªkd s kcZu dh rqyuk esa mPp vkf.od nzO;eku gksus osQ dkj.k gSykstu O;qRiUuksa esa izcy varjkvkf.od vkd"kZ.k cy (f}èkzoq &f}èkzoq rFkk okUMjokYl) gksrs gSAa ;gh dkj.k gS fd DyksjkbMks]a czkes kbMksa rFkk vk;ksMkbMksa osQ DoFkukad lerqY; nzO;eku okys gkbMªkd s kcZuksa osQ DoFkukadksa dh vis{kk egRoiw.kZ :i ls vfèkd gksrs gSAa v.kqvksa dk vkdkj cM+k gksus ij rFkk vfèkd la[;k esa bysDVªkWu mifLFkr gksus ij vkd"kZ.k cy vkSj vfèkd izcy gks tkrs gSaA fp=k 6-1 esa fofHkUu gSykbMksa osQ DoFkukadksa esa ifjorZu dk izk:i fn;k x;k gSA leku ,sfYdy lewg osQ fy, ,sfYdy gSykbMksa osQ DoFkukadksa osQ ?kVus dk Øe μ RI > RBr > RCl > R–F gSA ,slk gSykstu ijek.kq osQ vkdkj rFkk nzO;eku esa o`f¼ gksus ls okUMjokYl cyksa osQ ifjek.k esa o`f¼ gksus osQ dkj.k gksrk gSA fp=k 6-1 oqQN ,sfYdy gSykbMksa osQ DoFkukadksa dh rqyuk leko;oh gSyks,sYosQuksa esa Ük`a[kyu c Secondary halide > Tertiary halide. Fig.6.3: Steric effects in S N2 reaction. The relative rate of SN2 reaction is given in parenthesis (b) Substitution nucleophilic unimolecular (SN1) SN1 reactions are generally carried out in polar protic solvents (like water, alcohol, acetic acid, etc.). The reaction between tert- butyl bromide and hydroxide ion yields tert-butyl alcohol and follows the first order kinetics, i.e., the rate of reaction depends upon the concentration of only one reactant, which is tert- butyl bromide. It occurs in two steps. In step I, the polarised C—Br bond undergoes slow cleavage to produce a carbocation and a bromide ion. The carbocation thus formed is then attacked by nucleophile in step II to complete the substitution reaction. Step I is the slowest and reversible. It involves the C–Br bond breaking for which the energy is obtained through solvation of halide ion with the proton of protic solvent. Since the rate of reaction depends upon the slowest step, the rate of reaction depends only on the Haloalkanes and Haloarenes 177 fu%'kqYd forj.k] 2024&25 esfFky gSykbM lcls vfèkd 'kh?kzrk ls SN2 vfHkfØ;k nsrk gS D;ksafd blesa osQoy rhu NksVs gkbMªkstu ijek.kq gksrs gSaA r`rh;d ,sfYdy gSykbM lcls de fØ;k'khy gksrs gSa D;ksafd LFkwy lewg vkxeudkjh ukfHkdjkxh osQ fy, vojksèk mRiUu djrs gSa (fp=k 6-3)A vr% vfHkfØ;k'khyrk dk Øe fuEufyf[kr gksrk gSμ izkFkfed gSykbM > f}rh;d gSykbM > r`rh;d gSykbM fp=k 6-3 SN2 vfHkfØ;k esa f=kfoe izHkko] SN2 vfHkfØ;k osQ rqyukRed osx dks"Bd esa fn, gSaA ([k) ,dkf.od ukfHkdjkxh izfrLFkkiu (SN1) SN1 vfHkfØ;k,a lkekU;r% èkzqoh; izksfVd foyk;dksa (tSls ty] ,sYdksgkWy] ,slhfVd vEy vkfn) esa laiUu gksrh gSaA r`rh;d&C;wfVy czksekbM rFkk gkbMªkWDlkbM vk;u osQ eè; vfHkfØ;k r`rh;d&C;wfVy ,sYdksgkWy nsrh gS ,oa izFke dksfV dh cyxfrdh dk vuqlj.k djrh gSA vFkkZr~ vfHkfØ;k dk osx osQoy ,d vfHkfØ;d dh lkanzrk ij fuHkZj djrk gS] tks fd r`rh;d&C;wfVy czksekbM gSA ;g nks pj.kksa esa laiUu gksrh gSA izFke pj.k esa èkzqoh; C-Br vkcaèk dk èkhek fonyu ,d dkcksZoSQVk;u rFkk ,d czksekbM vk;u curk gSA f}rh; pj.k esa bl izdkj fufeZr dkcksoZ QS Vk;u ij ukfHkdjkxh osQ }kjk vkØe.k gksrk gS rFkk izfrLFkkiu vfHkfØ;k iw.kZ gksrh gSA pj.k&1 lcls èkhek rFkk mRØe.kh; gksrk gS blesa C–Br vkcaèk dk fonyu gksrk gS ftlosQ fy, ÅtkZ izksfVd foyk;dksa osQ izksVkWu }kjk gSykbM vk;u osQ foyk;d ;kstu ls izkIr gksrh gSA pw¡fd vfHkfØ;k dh nj lcls èkhes pj.k ij fuHkZj djrh gS] vr% vfHkfØ;k dk osx osQoy ,sfYdy gSykbM dh lkanzrk ij fuHkZj djrk gS] u fd gkbMªkWDlkbM vk;u dh lkanzrk ijA blosQ vfrfjDr dkcksZoSQVk;u dk LFkkf;Ro ftruk vfèkd gksxk] ,sfYdy gSykbM ls bldk fojpu mruk gh ljy gksxk rFkk vfHkfØ;k dk osx mruk gh vfèkd 177 gSyks,sYosQu rFkk gSyks,sjhu Free Distribution, 2024-25 concentration of alkyl halide and not on the concentration of hydr oxide ion. Further, greater the stability of carbocation, greater will be its ease of formation from alkyl halide and faster will be the rate of reaction. In case of alkyl halides, 3 0 alkyl halides undergo S N1 reaction 0 very fast because of the high stability of 3 carbocations. We can sum up the order of r eactivity of alkyl halides towards S N1 and S N2 reactions as follows: For the same reasons, allylic and benzylic halides show high reactivity towards the S N1 reaction. The carbocation thus formed gets stabilised through resonance (Unit 8, Class XI) as shown below: + + H2C C CH2 H2C C CH2 H H For a given alkyl group, the reactivity of the halide, R-X, follows the same order in both the mechanisms R–I> R–Br>R–Cl>>R–F. In the following pairs of halogen compounds, which would undergo Example 6.6 SN2 reaction faster? It is primary halide and therefore undergoes SN2 Solution reaction faster. As iodine is a better leaving group because of its large size, it will be released at a faster rate in the presence of incoming nucleophile. Predict the order of reactivity of the following Example 6.7 compounds in SN1 and SN2 reactions: (i) The four isomeric bromobutanes (ii) C6H5CH2Br, C6H5CH(C6H5)Br, C6H5CH(CH3)Br, C6H5C(CH3)(C6H5)Br Solution (i) CH3CH2CH2CH2Br < (CH3)2CHCH2Br < CH3CH2CH(Br)CH3 < (CH3)3CBr (SN1) CH3CH2CH2CH2Br > (CH3)2CHCH2Br > CH3CH2CH(Br)CH3 > (CH3)3CBr (SN2) Of the two primary bromides, the carbocation intermediate derived from (CH3)2CHCH2Br is more stable than derived from CH3CH2CH2CH2Br because of greater electron donating inductive effect of (CH3)2CH- group. Therefore, (CH3)2CHCH2Br is more reactive than CH3CH2CH2CH2Br in SN1 reactions. CH3CH2CH(Br)CH3 is a secondary bromide and (CH3)3CBr is a tertiary Chemistry 178 fu%'kqYd forj.k] 2024&25 gksxkA ,sfYdy gSykbMksa esa 3 ,sfYdy gSykbM] rhozrk ls SN1 vfHkfØ;k nsrs gSa D;ksafd 3 dkcksZoSQVk;u dk LFkkf;Ro lokZfèkd gksrk gSA ge SN1 rFkk SN2 vfHkfØ;k osQ fy, ,sfYdy gSykbM oQh fØ;k'khyrk osQ Øe dks la{ksi esa fuEu izdkj ls ns ldrs gSaμ bUgha dkj.kksa ls ,sfyfyd rFkk csfU”kfyd gSykbM SN1 vfHkfØ;k osQ izfr vfèkd fØ;k'khyrk izn£'kr djrs gSaA bl izdkj fu£er dkcksZoSQVk;u vuqukn osQ }kjk LFkkf;Ro izkIr dj ysrk gS tSlk fd uhps n'kkZ;k x;k gSµ nksuksa fØ;kfofèk;ksa esa fn, gq, ,sfYdy lewg osQ fy,] gSykbM R-X dh fØ;k'khyrk dk Øe bl izdkj gksrk gSμ R–I > R– Br > R–Cl > R–F. mnkgj.k 6.6 fuEufyf[kr gSykstu ;kSfxdksa osQ ;qxyksa esa dkSu lk ;kSfxd SN2 vfHkfØ;k rhozrk ls nsxk\ gy _ ;g izkFkfed gSykbM gS vr% SN2 vfHkfØ;k rhozrk ls nsrk gSA + _ cM+s vkdkj osQ dkj.k vk;ksMhu csgrj vof'k"V lewg gS vr% vkus okys ukfHkdjkxh dh mifLFkfr esa nzqr osx ls fudy tk,xkA mnkgj.k 6.7 SN1 o SN2 vfHkfØ;k esa fuEufyf[kr ;kSfxdksa dh vfHkfØ;k'khyrk dk Øe vuqekfur dhft,A (i) czkseksC;wVsu osQ pkj leko;oh (ii) C6H5CH2Br, C6H5CH(C6H5)Br, C6H5CH(CH3)Br, C6H5C(CH3)C6H5Br gy (i) CH3CH2CH2CH2Br CH3CH2CH(Br)CH3>(CH3)3CBr (SN2) (CH3)2CH– lewg osQ bysDVªku W nkrk izjs f.kd izHkko osQ vfèkd gksus osQ dkj.k nks izkFkfed czkes kbMksa esa ls (CH3)2CHCH2Br ls fufeZr eè;orhZ dkcksoZ QS Vk;u] CH3CH2CH2CH2Br ls cus dkcksZoSQVk;u dh vis{kk vfèkd LFkk;h gksxkA vr% SN1 vfHkfØ;k esa CH3CH2CH2CH2Br dh vis{kk (CH3)2CHCH2Br vfèkd fØ;k'khy gksrk gSA CH3CH2CH(Br)CH3 ,d f}rh;d czke s kbM gSA tcfd (CH3)3CBr r`rh;d czkes kbM 178 jlk;u foKku Free Distribution, 2024-25 bromide. Hence the above order is followed in S N1. The reactivity in SN2 reactions follows the reverse order as the steric hinderance around the electrophilic carbon increases in that order. (ii) C6H5C(CH3)(C6H5)Br > C6H5CH(C6H5)Br > C6H5CH(CH3)Br > C6H5CH2Br (SN1) C6H5C(CH3)(C6H5)Br < C6H5CH(C6H5)Br < C6H5CH(CH3)Br < C6H5CH2Br (SN2) Of the two secondary bromides, the carbocation intermediate obtained from C6H5CH(C6H5)Br is more stable than obtained from C6H5CH(CH3)Br because it is stabilised by two phenyl groups due to resonance. Therefore, the former bromide is more reactive than the latter in SN1 reactions. A phenyl group is bulkier than a methyl group. Therefore, C6H5CH(C6H5)Br is less reactive than C6H5CH(CH3)Br in SN2 reactions. (c) Stereochemical aspects of nucleophilic substitution reactions In order to understand the stereochemical aspects of substitution reactions, we need to learn some basic stereochemical principles and notations (optical activity, chirality, retention, inversion, racemisation, etc.). William Nicol (1768- (i) Optical activity: Plane of plane polarised light produced by passing 1851) developed the first ordinary light through Nicol prism is rotated when it is passed prism that produced through the solutions of certain compounds. Such compounds plane polarised light. are called optically active compounds. The angle by which the plane polarised light is rotated is measured by an instrument called polarimeter. If the compound rotates the plane of plane polarised light to the right, i.e., clockwise direction, it is called dextrorotatory (Greek for right rotating) or the d-form and is indicated by placing a positive (+) sign before the degree of rotation. If the light is rotated towards left (anticlockwise direction), the compound is said to be laevo-rotatory or the l-form and a negative (–) sign is placed before the degree of rotation. Such (+) and (–) isomers of a compound are called optical isomers and the phenomenon is termed as optical isomerism. (ii) Molecular asymmetry, chirality and enantiomers : The observation of Louis Pasteur (1848) that crystals of certain compounds exist in the form of mirror images laid the foundation of modern stereochemistry. He demonstrated that Jacobus Hendricus aqueous solutions of both types of crystals showed optical Van’t Hoff (1852-1911) rotation, equal in magnitude (for solution of equal received the first Nobel concentration) but opposite in direction. He believed that this Prize in Chemistry in difference in optical activity was associated with the three 1901 for his work on dimensional arrangements of atoms in the molecules solutions. (conﬁgurations) of two types of crystals. Dutch scientist, J. Van’t Hoff and French scientist, C. Le Bel in the same year (1874), independently argued that the spatial arrangement of four groups (valencies) around a central carbon is tetrahedral and if all the substituents attached to that carbon are different, the mirror image of the molecule is not superimposed (overlapped) on the molecule; such a carbon is called asymmetric carbon or stereocentre. The resulting molecule would lack symmetry and is referred to as asymmetric Haloalkanes and Haloarenes 179 fu%'kqYd forj.k] 2024&25 gS] vr% SN1 vfHkfØ;k osQ fy, vfHkfØ;k'khyrk dk Øe mijksDr gksrk gSA SN2 vfHkfØ;k esa mi;qZDr vfHkfØ;k'khyrk dk Øe foijhr gks tkrk gS] D;ksafd bysDVªkWu jkxh dkcZu ij f=kfoe ckèkk blh Øe esa c C6H5CH(C6H5)Br> C6H5CH(CH3)Br> C6H5CH2Br(SN1) C6H5C(CH3)(C6H5)Br< C6H5CH(C6H5)Br< C6H5CH(CH3)Br< C6H5CH2Br(SN2) nksuksa f}rh;d czksekbMksa esa ls] C6H5CH (C6H5)Br ls izkIr dkcksZoSQVk;u ekè;fed] C6H5CH (CH3)Br ls izkIr gksus okys ekè;fed dh vis{kk vfèkd LFkk;h gksrk gS] D;ksafd ;g nks i+sQfuy lewgksa }kjk vuqukn osQ dkj.k LFkkf;Ro izkIr dj ysrk gSA blfy,] igyk czksekbM nwljs dh vis{kk SN1 vfHkfØ;kvksa esa vfèkd fØ;k'khy gksrk gSA I k+ sQfuy lewg esfFky lewg ls vfèkd LFkwy gksrk gS] blfy, SN2 vfHkfØ;kvksa esa C6H5CH (C6H5)Br, C6H5CH (CH3)Br dh vis{kk de fØ;k'khy gksrk gSA (x) ukfHkdjkxh izfrLFkkiu vfHkfØ;kvksa osQ f=kfoe jklk;fud igyw ukfHkdjkxh izfrLFkkiu vfHkfØ;kvksa osQ f=kfoe jklk;fud igyw dks le>us osQ fy, gesa oqQN ewyHkwr f=kfoe&jklk;fud fl¼karksa rFkk izrhdksa (èkzqo.k ?kw.kZdrk] dkbjyrk] èkkj.k] izfrykseu rFkk jsflehdj.k vkfn) dks lh[kuk gksxkA fofy;e fudkWy (1768&1851) us (i) èkzqo.k ?kw.kZdrkµoqQN ;kSfxdksa osQ foy;u esa ls lery èkzqfor izdk'k xq”kkjs lery /zqfor izdk'k mRiUu djus tkus ij (tks fd lkekU; izdk'k dks fudkWy fiz”e ls xq”kkjus ij izkIr gksrk gS) okyk igyk fiz”e cuk;kA ;g bl izdk'k osQ ry dks ?kwf.kZr dj nsrs gSaA bl izdkj osQ ;kSfxdksa dks èkzqo.k ?kw.kZd ;kSfxd dgrs gSaA ml dks.k dks ftl ij èkzqfor izdk'k dk ry ?kw£.kr gks tkrk gS] èkzqo.kekih uked midj.k osQ }kjk ekik tk ldrk gSA ;fn ;kSfxd lery èkzqfor izdk'k osQ ry dks nkb± vksj ?kqek nsrk gS vFkkZr~ ?kM+h dh lqbZ dh fn'kk esa ?kqek nsrk gS rks mls nf{k.k èkzqo.k ?kw.kZd (xzhd esa nkfguh vksj ?kw.kZu) vFkok d :i dgrs gSa rFkk bls ?kw.kZu dks.k ls iwoZ èkukRed (+) fpÉ }kjk iznf'kZr djrs gSaA ;fn izdk'k dk ry ckb± vksj ?kwf.kZr gksrk gS] vFkkZr~ ?kM+h dh lwbZ osQ foijhr fn'kk esa] rks ;kSfxd dks oke èkzqo.k èkw.kZd vFkok l :i dgrs gSa rFkk ?kw.kZu dks.k ls iwoZ ½.kkRed (–) fpÉ yxkrs gSaA bl izdkj osQ (+) rFkk (–) leko;fo;ksa dks èkzqo.k leko;oh dgrs gSa rFkk bl ifj?kVuk dks èkzqo.k leko;ork dgrs gSaA tSdCl gSfUMªDl okUV gkWiQ (ii) vkf.od vleferrk] dkbjyrk ,oa izfr¯cc :iµyqbl ik'pj (1848) (1852&1911) us 1901 esa foy;uksa osQ bl izs{k.k us vkèkqfud f=kfoe jlk;u dh vkèkkjf'kyk j[kh fd oqQN ;kSfxdksa ij vius dk;Z osQ fy, jlk;u dk osQ fØLVy] niZ.k izfr¯cc :iksa esa ik, tkrs gSaA mUgksaus iznf'kZr fd;k fd nksuksa izFke ukscsy iqjLdkj izkIr fd;kA izdkj osQ fØLVyksa osQ leku lkanzrk okys tyh; foy;u] leku ifjek.k] ¯drq foijhr fn'kk esa èkzqo.k ?kw.kZu iznf'kZr djrs gSaA mudks fo'okl Fkk fd nksuksa izdkj osQ fØLVyksa osQ /wzo.k ?kw.kZu esa varj buosQ v.kqvksa esa ijek.kqvksa dh rhuksa foekvksa esa fHkUu O;oLFkk (foU;kl) ls lacafèkr gksrk gSA Mp oSKkfud ts- okUV gkWiQ rFkk izQakfllh oSKkfud ys csy us mlh o"kZ (1874)] esa Lora=k :i ls dk;Z djrs gq, roZQ fn;k fd osaQnzh; dkcZu ijek.kq osQ pkjksa vksj] lewgksa (la;kstdrkvksa) dh f=kfoe O;oLFkk prq"iQydh; gksrh gS vkSj ;fn dkcZu ijek.kq ls tqM+s lHkh izfrLFkkih fHkUu gksa rks v.kq dk niZ.k izfrfcac v.kq ij vè;kjksfir ugha gksrkA ,sls dkcZu ijek.kq dks vlefer dkcZu ijek.kq vFkok f=kfoeosaQnz dgrs gSaA ifj.kkeh v.kq dh leferrk Hkax gks tkrh gS rFkk bls vlefer v.kq dgrs gSaA v.kq dh vleferrk rFkk niZ.k 179 gSyks,sYosQu rFkk gSyks,sjhu Free Distribution, 2024-25 molecule. The asymmetry of the molecule along with non superimposability of mirror images is responsible for the optical activity in such organic compounds. The symmetry and asymmetry are also observed in many day to day objects: a sphere, a cube, a cone, are all identical to their mirror images and can be superimposed. However, many objects are non superimposable on their mirror images. For example, your left and right hand look similar but if you put your left hand on your right hand by moving them in the same plane, they do not coincide. The objects which are non- superimposable on their mirror image (like a pair of hands) are said to bechiral and this property is known as chirality. Chiral molecules are optically active, while the objects, which are, superimposable on their mirror images are called achiral. These molecules are optically inactive. The above test of molecular chirality can be applied to organic molecules by constructing models and its mirror images or by drawing three dimensional structures and attempting to superimpose them in our minds. There are other aids, however, that can assist us in recognising Fig 6.4: Some common examples of chiral and chiral molecules. One such aid is the presence of achiral objects a single asymmetric carbon atom. Let us consider two simple molecules propan-2-ol (Fig.6.5) and butan-2-ol (Fig.6.6) and their mirror images. Fig 6.5: B is mirror image of A; B is rotated by 180o and C is obtained; C is superimposable on A. As you can see very clearly, propan-2-ol (A) does not contain an asymmetric carbon, as all the four groups attached to the tetrahedral carbon are not different. We rotate the mirror image (B) of the molecule by 180° (structure C) and try to overlap the structure (C) with the structure (A), these structures completely overlap. Thus propan-2-ol is an achiral molecule. Butan-2-ol has four different groups attached to the tetrahedral carbon and as expected is chiral. Some common examples of chiral molecules such as 2-chlorobutane, 2, 3-dihyroxypropanal, (OHC–CHOH–CH 2 OH), bromochloro-iodomethane (BrClCHI), 2- bromopropanoic acid (H3C–CHBr–COOH), etc. Chemistry 180 fu%'kqYd forj.k] 2024&25 izfrfcac dk v.kq ij vè;kjksfir u gksuk bl izdkj osQ dkcZfud ;kSfxdksa esa èkzoq.k ?kw.kZu osQ fy, mÙkjnk;h gksrh gSA leferRkk rFkk vleferrk gekjs nSfud thou esa dke vkus okyh oLrqvksa esa Hkh ns[kus dks feyrh gSA xksys] ?ku] 'kaoqQ] Xyksc vkfn lHkh osQ niZ.k izfr¯cc muosQ leku gksrs gSa rFkk ;s niZ.k izfr¯cc ij vè;kjksfir fd, tk ldrs gSaA rFkkfi cgqr lh oLrq,a vius niZ.k izfr¯cc ij vè;kjksfir ugha gksrhaA mnkgj.kkFkZ] vkidk ck;k¡ rFkk nk;k¡ gkFk leku fn[kkbZ nsrk gS_ ysfdu ;fn vki vius ck,a gkFk dks nkfgus gkFk ij mlh lery esa ys tkrs gq, j[ksa rks nksuksa ,d nwljs dks Bhd&Bhd ugha kb,A 6.8 gSykstu ;kSfxdksa osQ fuEufyf[kr ;qxyksa esa ls dkSu lk ;kSfxd rhozrkSls N 1 vfHkfØ;k djsxk\ 6.9 fuEufyf[kr esa A, B, C, D, E, R rFkk R1 dks igpkfu,μ 3- èkkrqvksa osQ lkFk vfHkfØ;k oqVZ~t&fiQfVx vfHkfØ;kµ ,sfYdy gSykbM rFkk ,sfjy gSykbM dk feJ.k] lksfM;e osQ lkFk 'kq"d bZFkj dh mifLFkfr esa xje djus ij ,sfYdy,sjhu nsrk gS rFkk bls oqVZ~t&fiQfVx vfHkfØ;k dgrs gSaA 190 jlk;u foKku Free Distribution, 2024-25 Fittig reaction Aryl halides also give analogous compounds when treated with sodium in dry ether, in which two aryl groups are joined together. It is called Fittig reaction. 6. 8 Polyhalogen Carbon compounds containing more than one halogen atom are usually referred to as polyhalogen compounds. Many of these Compounds compounds are useful in industry and agriculture. Some polyhalogen compounds are described in this section. 6.8.1 Dichloro- Dichloromethane is widely used as a solvent as a paint remover, as a methane propellant in aerosols, and as a process solvent in the manufacture of (Methylene drugs. It is also used as a metal cleaning and ﬁnishing solvent. chloride) Methylene chloride harms the human central nervous system. Exposure to lower levels of methylene chloride in air can lead to slightly impaired hearing and vision. Higher levels of methylene chloride in air cause dizziness, nausea, tingling and numbness in the ﬁngers and toes. In humans, direct skin contact with methylene chloride causes intense burning and mild redness of the skin. Direct contact with the eyes can burn the cornea. 6.8.2 Trichloro- methane Chemically, chloroform is employed as a solvent for fats, alkaloids, (Chloroform) iodine and other substances. The major use of chloroform today is in the production of the freon refrigerant R-22. It was once used as a general anaesthetic in surgery but has been replaced by less toxic, safer anaesthetics, such as ether. As might be expected from its use as an anaesthetic, inhaling chloroform vapours depresses the central nervous system. Breathing about 900 parts of chloroform per million parts of air (900 parts per million) for a short time can cause dizziness, fatigue, and headache. Chronic chloroform exposure may cause damage to the liver (where chloroform is metabolised to phosgene) and to the kidneys, and some people develop sores when the skin is immersed in chloroform. Chloroform is slowly oxidised by air in the presence of light to an extremely poisonous gas, carbonyl chloride, also known as phosgene. It is therefore stored in closed dark coloured bottles completely ﬁlled so that air is kept out. 6.8.3 Triiodo- It was used earlier as an antiseptic but the antiseptic properties are methane due to the liberation of free iodine and not due to iodoform itself. Due to (Iodoform) its objectionable smell, it has been replaced by other formulations containing iodine. 6.8.4 Tetrachlo- It is produced in large quantities for use in the manufacture of romethane refrigerants and propellants for aerosol cans. It is also used as (Carbon feedstock in the synthesis of chloroﬂuorocarbons and other chemicals, tetrachloride) pharmaceutical manufacturing, and general solvent use. Until the mid Haloalkanes and Haloarenes 191 fu%'kqYd forj.k] 2024&25 fiQfVx vfHkfØ;kµ,sfjy gSykbM Hkh 'kq"d bZFkj esa lksfM;e osQ lkFk vfHkfØ;k }kjk ltkrh; ;kSfxd nsrs gSa] ftlesa nks ,sfjy lewg ijLij tqM+s jgrs gSaA blsfiQfVx vfHkfØ;k dgrs gSaA 6-8 ikWfygSykstu ,d ls vfèkd gSykstu ijek.kq;Dq r ;kSfxd lkekU;r% ikWfygSykstu ;kSfxd dgykrs gSAa buesa ls vusd ;kSfxd m|ksxksa rFkk Ñf"k esa mi;ksxh gSaA bl [kaM esa oqQN egRoiw.kZ ikWfygSykstu ;kSfxd ;kSfxdksa dk o.kZu fd;k x;k gSA 6-8-1 MkbDyksjksesFksu MkbDyksjksesFksu dk vR;fèkd mi;ksx foyk;d osQ :i esa] isaV vi;ud esa] ,sjkslkWy esa (esfFkyhu iz.kksnd osQ :i esa rFkk vkS"kèk fuekZ.k dh izfØ;k esa foyk;d osQ :i esa gksrk gSA ;g + ,oa fiQfuf'kax foyk;d osQ :i esa iz;qDr gksrk gSA esfFkyhu DyksjkbM èkkrq dh lIkQkbZ DyksjkbM) euq";ksa osQ osaQnzh; raf=kdk ra=k dks gkfu igq¡pkrk gSA ok;q esa esfFkyhu DyksjkbM oQh FkksM+h lh ek=kk osQ lEioZQ esa vkus osQ izHkko ls Jo.k ,oa n`'; {kerk esa vkaf'kd {kh.krk vkrh gSA esfFkyhu DyksjkbM oQh ok;q esa vfèkd ek=kk osQ izHkko ls pDdj vkuk] feryh] gkFk&iSjksa dh vaxqfy;ksa esa luluh ,oa tM+rk vkfn y{k.k mRiUu gks tkrs gSaA euq";ksa esa esfFkyhu DyksjkbM osQ Ropk osQ lhèks laioZQ esa vkus ij rhoz tyu rFkk gYdk ykyiu vk tkrk gSA vk¡[kksa ls lhèkk laioZQ dksfuZ;k tyk ldrk gSA 6-8-2 VªkbDyksjksesFksu jklk;fud :i esa DyksjksiQkeZ dk mi;ksx olk] ,sYosQykWbM] vk;ksMhu rFkk vU; inkFkks± osQ (DyksjksiQkeZ) fy, foyk;d osQ :i esa gksrk gSA orZeku esa DyksjksiQkeZ dk izeq[k mi;ksx iszQvkWu iz'khrd R-22 cukus esa gksrk gSA igys bldk mi;ksx 'kY; fpfdRlk esa fu'psrd osQ :i esa gksrk Fkk_ ijarq vc bldk LFkku bZFkj tSls de fo"kSys ,oa vfèkd lqjf{kr fu'psrdksa us ys fy;k gSA fu'psrd osQ :i esa blosQ mi;ksx dks ns[krs gq, ;g visf{kr gS fd DyksjksiQkWeZ dks lw?¡ kus ls osaQnzh; raf=kdk ra=k voufer gks tkrk gSA ok;q osQ izfr nl yk[k Hkkx esa 900 Hkkx DyksjksiQkWeZ (900 Hkkx izfr nl yk[k) esa cgqr de le; rd lkal ysus ls pDdj] Fkdku ,oa fljnnZ gks ldrk gS] DyksjksiQkWeZ osQ nh?kZdkfyd laioZQ (exposure) ls ;Ñr dk (tgk¡ DyksjksiQkeZ i+QkWLthu esa mikipf;r gksrh gS) ,oa o`Dd dk {k; gks ldrk gS rFkk oqQN O;fDr;ksa dh Ropk DyksjksiQkeZ esa Mwch jgus ij mlesa ?kko gks tkrs gSaA DyksjksiQkWeZ izdk'k dh mifLFkfr esa ok;q }kjk èkhjs&èkhjs vkWDlhÑr gksdj vR;fèkd fo"kSyh xSl] dkcksZfuy DyksjkbM cukrh gS ftls i+QkWLthu Hkh dgrs gSaA blfy, HkaMkj.k osQ fy, bls iw.kZr% Hkjh gqbZ bls jaxhu cksryksa esa j[kk tkrk gS rkfd muesa ok;q u jgsA 6-8-3 Vªkbvk;ksMksesFksu bldk mi;ksx izkjaHk esa iwfrjksèkh (,safVlsfIVd) osQ :i esa fd;k tkrk Fkk ijarq vk;MksiQkWeZ (vk;MksiQkeZ) dk ;g iwfrjksèkh xq.k vk;MksiQkeZ osQ dkj.k Lo;a ugha] cfYd eqDr gqbZ vk;ksMhu osQ dkj.k gksrk gSA bldh v#fpdj xaèk osQ dkj.k vc blosQ LFkku ij vk;ksMhu ;qDr vU; nokvksa dk mi;ksx fd;k tkrk gSA 6-8-4 VsVªkDyksjksesFksu bldk vR;fèkd ek=kk esa mRiknu iz'khrd cukus rFkk ,sjkslkWy oSQu osQ fy, iz.kksnd osQ (dkcZu mRiknu esa mi;ksx djus osQ fy, fd;k tkrk gS bls DyksjksÝyqvksjks dkcZu rFkk vU; jlk;uksa + osQ mRiknu easa Hkh I kQhMLVkW d dh rjg ,oa vkS"kèk mRiknu esa rFkk lkekU; foyk;d dh VsVªkDyksjkbM) Hkk¡fr iz;qDr fd;k tkrk gSA 1960 osQ eè; rd ;g m|ksxksa esa xzhl dks lkIkQ djus okys 191 gSyks,sYosQu rFkk gSyks,sjhu Free Distribution, 2024-25 as a degreasing agent, and in the home, as a spot remover and as ﬁre extinguisher. There is some evidence that exposure to carbon tetrachloride causes liver cancer in humans. The most common effects are dizziness, light headedness, nausea and vomiting, which can cause permanent damage to nerve cells. In severe cases, these effects can lead rapidly to stupor, coma, unconsciousness or death. Exposure to CCl can 4 make the heart beat irregularly or stop. The chemical may irritate the eyes on contact. When carbon tetrachloride is released into the air, it rises to the atmosphere and depletes the ozone layer. Depletion of the ozone layer is believed to increase human exposure to ultraviolet rays, leading to increased skin cancer, eye diseases and disorders, and possible disruption of the immune system. 6.8.5 Freons The chloroﬂuorocarbon compounds of methane and ethane are collectively known as freons. They are extremely stable, unreactive, non- toxic, non-corrosive and easily liqueﬁable gases. Freon 12 (CCl F ) is one of 2 2 the most common freons in industrial use. It is manufactured from tetrachloromethane by Swarts reaction. These are usually produced for aerosol propellants, refrigeration and air conditioning purposes. By 1974, total freon production in the world was about 2 billion pounds annually. Most freon, even that used in refrigeration, eventually makes its way into the atmosphere where it diffuses unchanged into the stratosphere. In stratosphere, freon is able to initiate radical chain reactions that can upset the natural ozone balance. 6.8.6 p,p’-Dichlo- DDT, the ﬁrst chlorinated organic insecticides, was originally prepared in rodiphenyl- 1873, but it was not until 1939 that Paul Muller of Geigy Pharmaceuticals trichloro- in Switzerland discovered the effectiveness of DDT as an insecticide. Paul ethane(DDT) Muller was awarded the Nobel Prize in Medicine and Physiology in 1948 for this discovery. The use of DDT increased enormously on a worldwide basis after World War II, primarily because of its effectiveness against the mosquito that spreads malaria and lice that carry typhus. However, problems related to extensive use of DDT began to appear in the late 1940s. Many species of insects developed resistance to DDT, and it was also discovered to have a high toxicity towards ﬁsh. The chemical stability of DDT and its fat solubility compounded the problem. DDT is not metabolised very rapidly by animals; instead, it is deposited and stored in the fatty tissues. If ingestion continues at a steady rate, DDT builds up within the animal over time. The use of DDT was banned in the United States in 1973, although it is still in use in some other parts of the world. Chemistry 192 fu%'kqYd forj.k] 2024&25 nzo rFkk ?kjksa esa nkx&èkCcs gVkus okys nzo ,oa vfXu 'kked osQ :i esa cgqrk;r ls iz;qDr gksrk FkkA bl izdkj osQ oqQN izek.k gSa fd dkcZu VsVªkDyksjkbM ls mn~Hkklu (exposure) }kjk euq";ksa dks ;Ñr dk oaSQlj gks tkrk gSA blosQ oqQN izeq[k izHkko gSa pDdj vkuk] flj dk gYdkiu] feryh rFkk mYVh vkuk vkfn] ftlls raf=kdk dksf'kdkvksa esa LFkk;h {kfr gks ldrh gSA xaHkhj fLFkfr esa ;g izHkko 'kh?kzrk ls ewPNkZ] xgjh uhan] csgks'kh vFkok e`R;q yk ldrk gSA CCl4 osQ mn~Hkklu ls ân;xfr vfu;fer gks ldrh gS vFkok #d tkrh gSA vk¡[kksa osQ laidZ esa vkus ij bl jlk;u ls tyu mRiUu gksrh gSA dkcZuVsVªkDyksjkbM ok;q esa fueqZDr gksus ij Åijh ok;qeaMy esa igq¡p tkrh gS vkSj vks”kksu ijr dks fojy cuk nsrh 6-8-5 izQs vkWu gSA vks”kksu ijr osQ fojyhdj.k ls euq";ksa dk ijkcSaxuh fdj.kksa ls mn~Hkklu ckb,A 6.21 izkFkfed ,sfYdy gSykbM C4H 9Br (d)] ,sYdksgkWfyd KOH esa vfHkfØ;k }kjk ;kSfxd ([k) nsrk gSA ;kSfxd ^[k* HBr osQ lkFk vfHkfØ;k ls ;kSfxd ^x* nsrk gS tks fd ;kSfxd ^d* dk leko;oh gSA tc ;kSfxd ^d* dh vfHkfØ;k lksfM;e èkkrq ls gksrh gS rks ;kSfxd ^?k* C8H 18 curk gS] tks fd C;wfVy czksekbM dh lksfM;e ls vfHkfØ;k }kjk cus mRikn ls fHkUu gSA ;kSfxd ^d* dk lajpuk lw=k nhft, rFkk lHkh vfHkfØ;kvksa dh lehdj.k nhft,A 6.22 rc D;k gksrk gS tcμ (i) n&C;wfVy DyksjkbM dks ,sYdksgkWfyd KOH osQ lkFk vfHkÑr fd;k tkrk gS\ (ii) 'kq"d bZFkj dh mifLFkfr esa czksekscsUthu dh vfHkfØ;k eSXuhf'k;e ls gksrh gS\ (iii) DyksjkscsUthu dk tyvi?kVu fd;k tkrk gS\ (iv) ,fFky DyksjkbM dh vfHkfØ;k tyh; KOH ls gksrh gS\ (v) 'kq"d bZFkj dh mifLFkfr esa esfFky czksekbM dh vfHkfØ;k lksfM;e ls gksrh gS\ (vi) esfFky DyksjkbM dh vfHkfØ;k KCN ls gksrh gS\ 195 gSyks,sYosQu rFkk gSyks,sjhu Free Distribution, 2024-25 Answers to Some Intext Questions 6.1 6.2 (i) H2SO4 cannot be used along with KI in the conversion of an alcohol to an alkyl iodide as it converts KI to corresponding acid, HI which is then oxidised by it to I2. 6.3 (i) ClCH2CH2CH2Cl (ii) ClCH 2CHClCH3 (iii) Cl 2CHCH2CH3 (iv) CH 3CCl2CH3 6.4 All the hydrogen atoms are equivalent and replacement of any hydrogen will give the same product. The equivalent hydrogens are grouped as a, b and c. The replacement of equivalent hydrogens will give the same product. Similarly the equivalent hydrogens are grouped as a, b, c and d. Thus, four isomeric products are possible. 6.5 6.6 (i) Chloromethane, Bromomethane, Dibromomethane, Bromoform. Boiling point increases with increase in molecular mass. (ii) Isopropylchloride, 1-Chloropropane, 1-Chlorobutane. Isopropylchloride being branched has lower b.p. than 1- Chloropropane. 6.7 (i) CH3CH2CH2CH2Br Being primary halide, there won’t be any steric hindrance. (ii) Secondary halide reacts faster than tertiary halide. (iii) The presence of methyl group closer to the halide group will increase the steric hindrance and decrease the rate. Chemistry 196 fu%'kqYd forj.k] 2024&25 dq N ikB~;fufgr iz'uksa ds mÙkj 6.1 6.2 (i) ,sYdksgkWy osQ ,sfYdy vk;ksMkbM esa ifjorZu osQ fy, KI osQ lkFk H2SO4 dk iz;ksx ugha fd;k tk ldrk_ D;ksafd ;g KI dks laxr HI vEy esa ifjofrZr dj nsrk gS] rRi'pkr~ bls I2 esa vkDlhÑr dj nsrk gSA 6.3 ClCH2CH2CH2Cl (II) ClCH2CHClCH3 (iii) Cl2CH2CH2CH3 (iv) CH3CCl2CH3 6.4 (i) pw¡fd lHkh gkbMªkstu ijek.kq lerqY; gSa] vr% fdlh Hkh gkbMªkstu ijek.kq osQ izfrLFkkiu ij leku mRikn cusxkA (ii) lerqY; gkbMªkstuksa dks a,b,c ls funsZf'kr fd;k x;k gSA lerqY; gkbMªkstuksa osQ izfrLFkkiu ij leku mRikn cusaxsaA (iii) blh izdkj lerqY; gkbMªkstuksa dks a, b, c rFkk d ls funsZf'kr fd;k x;k gS vr% pkj leko;oh mRikn laHko gSaA 6.5 6.6 (i) DyksjksesFksu < czkseksesFksu < MkbczkseksesFksu < czkseksiQkeZ v.kqHkkj cC=O) gksrk gS ftls dkcksZfuy lewg dgrs gSaA ;g dkcZfud jlk;u dk ,sfYMgkbMksa o dhVksuksa dh dqN p;fur ,d egRoiw.kZ izdk;kZRed lewg gSA vfHkfØ;kvksa dh fØ;kfof/ dks le>k losaQxsA ,sfYMgkbMksa esa dkcksZfuy lewg dkcZu o gkbMªkstu ls] tcfd dhVksuksa dkcksZfDlfyd vEyksa dh vEyrk dks izHkkfor esa ;g nks dkcZu ijek.kqvksa ls vkcaf/r jgrk gSA dkcksZfuy ;kSfxd ftuesa djus okys dkjdksa rFkk mudh vfHkfØ;kvksa dkcksZfuy lewg dk dkcZu] gkbMªkstu ;k dkcZu rFkk gkbMªkDlh ekbVh dks le> losaQxsA (– OH) dh vkWDlhtu ls vkcaf/r jgrk gS] dkcksZfDlfyd vEy dgykrs ,sfYMgkbMksa] dhVksuksa ,oa dkcksZfDlfyd vEyksa gSa tcfd os ;kSfxd ftuesa dkcksZfuy lewg dk dkcZu] gkbMªkstu ;k dkcZu osQ mi;ksxksa dk o.kZu dj losaQxsA rFkk – NH ekbVh osQ ukbVªkstu vFkok fdlh gSykstu ls tqM+k jgrk gS] 2 Øe'k% ,ekbM o ,sfly gSykbM dgykrs gSaA ,LVj vkSj ,ugkbMªkbM dkcksfZ Dlfyd vEyksa osQ O;qRiUu gksrs gSAa bu oxksaZ osQ ;kSfxdksa osQ lkekU; lw=k uhps fn, x, gS— a ,sfYMgkbM] dhVksu ,oa dkcksZfDlfyd vEy 233 Free Distribution : 2024-25 Aldehydes, ketones and carboxylic acids are widespread in plants and animal kingdom. They play an important role in biochemical processes of life. They add fragrance and flavour to nature, for example, vanillin (from vanilla beans), salicylaldehyde (from meadow sweet) and cinnamaldehyde (from cinnamon) have very pleasant fragrances. They are used in many food products and pharmaceuticals to add flavours. Some of these families are manufactured for use as solvents (i.e., acetone) and for preparing materials like adhesives, paints, resins, perfumes, plastics, fabrics, etc. 8.1 Nomenclature and Structure of Carbonyl Group 8.1.1 I. Aldehydes and ketones Nomenclature Aldehydes and ketones are the simplest and most important carbonyl compounds. There are two systems of nomenclature of aldehydes and ketones. (a) Common names Aldehydes and ketones are often called by their common names instead of IUPAC names. The common names of most aldehydes are derived from the common names of the corresponding carboxylic acids [Section 8.6.1] by replacing the ending –ic of acid with aldehyde. At the same time, the names reflect the Latin or Greek term for the original source of the acid or aldehyde. The location of the substituent in the carbon chain is indicated by Greek letters a, b, g, d, etc. The a-carbon being the one directly linked to the aldehyde group, b- carbon the next, and so on. For example Chemistry 234 fu%'kqYd forj.k % 2024&25 ,sfYMgkbM] dhVksu ,oa dkcksZfDlfyd vEy ikS/ksa vkSj thoksa esa foLr`r :i ls ik, tkrs gSaA ;s thoksa dh tSo jklk;fud izfØ;k esa egRoiw.kZ ;ksxnku nsrs gSaA ;s izÑfr esa lqxa/ o Lokn iznku djrs gSaA mnkgj.kkFkZ] osusfyu (csuhyk lse ls izkIr) lkSfyfly ,sfYMgkbM (esMksLohV ls izkIr) rFkk fluseSfYMgkbM (nky phuh ls izkIr) #fpdj lqxa/ nsrs gSaA ;s vusd [kk| mRiknksa o vkS"k/ksa esa lqxa/ iznku djus osQ fy, iz;qDr gksrs gSaA bl oxZ osQ dqN ;kSfxdksa dk mRiknu foyk;d (,slhVksu) vkSj vklath (fpioQus okys) inkFkZ] isaV] jsf”ku] lqxa/] IykfLVd] oL=k vkfn cukus osQ fy, fd;k tkrk gSA 8-1 dkcksfZ uy ;kSfxdksa dk ukedj.k ,oa lajpuk 8-1-1 ukei¼fr (I ) ,sfYMgkbM ,oa dhVksu ,sfYMgkbM ,oa dhVksu ljyre vkSj vR;ar egRoiw.kZ dkcksZfuy ;kSfxd gSaA ,sfYMgkbMksa ,oa dhVksuksa osQ ukedj.k dh nks i¼fr;k¡ gSaμ (d) lkekU; ukeµ ,sfYMgkbM ,oa dhVksu izk;% IUPAC ukei¼fr dh vis{kk vius lkekU; ukeksa ls tkus tkrs gSAa ,sfYMgkbM osQ lkekU; uke laxr dkcksfZ Dlfyd vEyksa ([kaM 8-6-1) osQ vaxzs”kh esa fy[ks lkekU; ukeksa osQ var esa fLFkr vuqyXu bd osQ LFkku ij ,sfYMgkbM vuqyXu yxkdj izkIr djrs gSaA lkFk gh dkcksZfDlfyd vEy ;k ,sfYMgkbM osQ uke esa okLrfod Ïksr dk uke ysfVu ;k xzhd esa izfr¯cfcr gksrk gSA dkcZu Üka`[kyk esa izfrLFkkfi;ksa dh fLFkfr dks xzhd v{kjksa a, b, g, d, vkfn ls iznf'kZr djrs gSaA a ml dkcZu ijek.kq dks dgrs gSa tks lhèks ,sfYMgkbM lewg osQ dkcZu ijek.kq ls layXu gksrk gSA rRi'pkr~ b dkcZu rFkk vU; blh Øe esa vkxs pyrs gSaA mnkgj.kkFkZμ 234 jlk;u foKku Free Distribution : 2024-25 The common names of ketones are derived by naming two alkyl or aryl groups bonded to the carbonyl group. The locations of substituents are indicated by Greek letters, a a¢, b b¢ and so on beginning with the carbon atoms next to th

Chemistry Textbook Part II PDF for Class XII

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