Which of the following statements are is correct?

Solution:

(a) The correct order is ${\mathrm{NH}}_3>{\mathrm{CH}}_3{\mathrm{CONH}}_2>{\left({\mathrm{CH}}_3\mathrm{CO}\right)}_2\mathrm{NH}$ In the anion from ammonia, the negative charge is localized on nitrogen. In the anion from acetamide, the negative charge is shared by nitrogen and one oxygen. In the anion from diacetamide, the negative charge is shared by nitrogen and two oxygens.

(b) p-Aminobenzoic acid does not exist as dipolar ion. An aromatic $-{\mathrm{NH}}_2$ group is a weak base and it cannot neutralize the $-\mathrm{COOH}$ group. It can, however, neutralize the stronger acidic $-{\mathrm{SO}}_3\mathrm{H}$ group. Thus, sulphanilic acid can exist as dipolar ion.

( d) In Hofmann elimination, a less substituted alkene is produced.