repulsion between the bulky methyl groups. 101Pm 101Pm Lone pair of electon sp hybrid sp - sp . . General methods of preparation Amines Aliphatic and aromatic amines are prepared by the following methods.
) From nitro compounds Reduction of Nitro compounds using H / Ni (or) Sn / HCl or Pd/H gives primary amines. CH CH NO 3H / Ni (or) Fe / HCl, [H] CH CH NH + H O Nitroethane ethanamine C H NO 3H / Pt, K (or) Sn / HCl Nitrobenzene C H NH + H O Aniline ) From nitriles a) Reduction of alkyl or aryl cyanides with H /Ni (or) LiAlH (or) Na / C H OH gives primary amines. The reduction reaction in which Na / C H OH is used as a reducing agent is called mendius reaction CN Na(Hg) / C H OH [ H ] CH CH NH ethanenitrile ethanamine b) Reduction of isocyanides with sodium amalgam / C H OH gives secondary amines NC Na(Hg) / C H OH [ H] NH Methyl isocyanide N-methylmethanamine XII U13-Organic Nitrogen XII U13-Organic Nitrogen - - - - ) From amides a) Reduction of amides with LiAlH gives amines R NH i) LiAlH ii) H O R NH b) Hoffmann’s degradation reaction When Amides are treated with bromine in the presence of aqueous or ethanolic solution of KOH, primary amines with one carbon atom less than the parent amides are obtained. Example: R R NH + K CO + KBr + H O NH Br / KOH amide R = Alkyl (or) Aryl Primary amine ) From alkyl halides a) Gabriel phthalimide synthesis Gabriel synthesis is used for the preparation of Aliphatic primary amines.
Phthalimide on treatment with ethanolic KOH forms potassium salt of phthalimide which on heating with