Question

(a) Write the reactions involved in the following :
(i) Hofmann bromamide degradation reaction.
(ii) Diazotisation .
(iii) Gabriel phthalimide synthesis
(b) Give reasons :
(i) `(CH_(3))_(2)NH` is more basic than `(CH_(3))_(3)N` in an aqueous solution.
(ii) Aromatic diazonium salts are more stable than aliphatic diazonium salts .

Answer 1

(a) (i) Hofmann bromamide degradation reaction :
`CH_(3)underset("Ethanamide")(CONH_(2) + ) Br_(2) + 4KOH to underset("Methanamine")(CH_(3)NH_(2) + )K_(2)CO_(3) + 2KBr + 2H_(2)O`
(ii) Diazotisation :

(iii) Gabriel Phthalinide synthesis :

(b) (i) `(CH_(3))_(2)NH` is more basic than `(CH_(3))_(3)N` in an aqeuous solution due to the following reasons :
Inductive effect (+I) : More are alkyl group , greater will be the inductive effect .
`therefore` basicity of `(CH_(3))_(3) N gt (CH_(3))_(2)NH`
Hydrogen bonding : Greater the H-bond , greater will be basicity . Hence `(CH_(3))_(2) NH gt (CH_(3))_(3)N` . Stability due to hydrogen bonding predominates over the stability due to inductive effect . Hence `(CH_(3))_(2)NH` is more basic than `(CH_(3))_(3)N`.
(ii) Aromatic diazonium salts are more stable than aliphatic diazoniom salt due to the dispersal of positive charge over the benzene ring.