a) Explain the following observations:
i) Electrophilic substitution in aromatic amines takes place more readily than in benzene.
ii) Primary amines boil higher than comparable tertiary amines.
b) Mention two important uses of N,N-dimethylaniline.
i) Electrophilic substitution in aromatic amines takes place more readily than in benzene.
ii) Primary amines boil higher than comparable tertiary amines.
b) Mention two important uses of N,N-dimethylaniline.
Solution
(a)(i) The nitrogen lone pair delocalises into the ring, raising electron density, especially ortho/para — electrophiles attack far faster than on benzene.
(ii) Primary amines hydrogen-bond through their two N–H's; tertiary amines cannot — so R–NH boils higher.
(b) N,N-Dimethylaniline is used (1) in making azo dyes such as methyl orange and butter yellow, and (2) as an intermediate/accelerator in dye and polymer chemistry.
(ii) Primary amines hydrogen-bond through their two N–H's; tertiary amines cannot — so R–NH boils higher.
(b) N,N-Dimethylaniline is used (1) in making azo dyes such as methyl orange and butter yellow, and (2) as an intermediate/accelerator in dye and polymer chemistry.
CBSE Class 12 Board · 2006 · Delhi; also All India · Subjective