The Total solution for NCERT class 6-12
Why cannot aromatic primary amines be prepared by Gabrielphthalimide synthesis?
Answer - 21 : -
Gabriel phthalimide synthesis is used forthe preparation of aliphatic primary amines. It involves nucleophilicsubstitution (SN2) of alkyl halides by the anion formed by thephthalimide.
But aryl halides do not undergo nucleophilic substitutionwith the anion formed by the phthalimide.
Hence, aromatic primary amines cannot be prepared by thisprocess.
Write the reactions of (i) aromaticand (ii) aliphatic primary amines with nitrous acid.
Answer - 22 : -
(i) Aromaticamines react with nitrous acid (prepared in situ from NaNO2 anda mineral acid such as HCl) at 273 − 278 K to form stable aromatic diazoniumsalts i.e., NaCl and H2O.
(ii) Aliphaticprimary amines react with nitrous acid (prepared in situ from NaNO2 anda mineral acid such as HCl) to form unstable aliphatic diazonium salts, whichfurther produce alcohol and HCl with the evolution of N2 gas.