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1|Page, , Chemistry Notes for class 12 Chapter 13, Amines, , Amines constitute an important class of organic compounds derived by replacing one or more, hydrogen atoms ofNH 3 molecule by alkyl/aryl group(s)., , R—NH, R—NH—R R—N—R C,H, —NH,, primary (1°) —_ secotidary (2°) aromatic amine, , R, tertiary (8°), In the IUPAC system, the amines are regarded as alkanamines, e.g.,, pi, —cH, NH, CH,CH,—NH—CH, CH, —CH,—NZ, ethanamine N-methyl ethanamine “Oakly, N,N-diethylothanaming, Structure, , The nitrogen atom in amine is spa-hybridised. ‘The three hybrid orbitals are involved in bond, formation and one hybrid atomic orbital contains the lone pair of electrons, giving the, pyramidal geometry of amines., , Bassiomines Na group is directly attached to the benzene ring., N(CHys, , go O, , (N,N.dimethylbenzenamine), , Methods of Preparation of Amines

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4|Page, , 5. Tertiary amines does not have intermolecular association due to the absence of hydrogen, atom available for hydrogen bond formation., , Basic Strength of Amines, , Amines act as Lewis bases due to the presence of lone pair of electrons on the nitrogen atom., More the Ky (dissociation constant of base), higher is the basicity of amines., , Lesser the pK," higher is the basicity of amines., , Aliphatic amines (CH;NH)) are stronger bases than NH; due to the electron releasing +/ effect, of the alkyl group., , Among aliphatic methyl amines, the order of basic strength in aqueous solution is as follows, (CoHsNH > (CH;);N > CoHsNH> > NH;, (CH;),.NH > CH3NH; > (CH;);N > NH;, , Aromatic amines are weaker basesthan aliphatic amlnes and NH3,due to the fact that the, electron pair on the nitrogen atom is involved in resonance with the z-electron pairs of the ring., , Electron releasing groups (¢.g.,-CH;,-OCH3,-NH) etc.) increase the basic strength of aromatic, amines while electron withdrawing groups (like — NO:, -X,-CN etc.) tend to decrease the same., , o-substituted aromaticamines are usually weaker basesthan aniline irrespective of the nature of, substituent whether electron releasing or electron withdrawing. This is called ortho effect and is, probably due to sterk and electronic factors., , chemical Properties of Amines, , (i) Alkylation All the three types of amines react with alkyl halides to form quaternary, ammonium salt as the final product provided alkyl] halide is present in excess., , C,H,NH, +C,H,Br —=, (C,H,),NH — =, , (CH; ig, | C,H,Br, +, (CgH;),NBr, , Aromatic amines also undergo alkylation as given below., , Scanned with Cases