Question

Explain the following named reactions:

(i) Sandmeyer reaction
(ii) Gattermann reaction

Answer 1

(a) Gattermann reaction:
Formylation of aromatic compounds with $HCN$ in presence of $AlC{l}_3$ is carried out. We can also use $Zn(CN{)}_2$ instead of $HCl/AlC{l}_3$.
$C_6{H}_6\underset{\left(ii\right)H_{2}O,-N{H}_{4}Cl}{\overset{\left(i\right)HCN/AlC{l}_3}{\to }}{C}_6{H}_5-CHO$
(b) Sandmeyer reaction:
It converts aryl diazonium salts to aryl halides. An aromatic amino group is substitued with a nucleophile (such as halide anions, cyanide, thiols, water, and others) via diazonium salt intermediate. The reaction is catalyzed by cuprous compounds.
$Ph{N}_2^{+}C{l}^{-}\underset{-N_2}{\overset{CuCl}{\to }}Ph-Cl$