Explain the method of preparation of aldehydes and ketones from nitrile compounds.

(N/A) Preparation of aldehyde from nitrile compounds by Stephen reduction reaction:
Nitriles are reduced to the corresponding imine with stannous chloride $(SnCl_2)$ in the presence of hydrochloric acid $(HCl)$,which on hydrolysis gives the corresponding aldehyde. This reaction is called the Stephen reaction.
$RC \equiv N + SnCl_2 + HCl$ $\rightarrow RCH = NH$ $\xrightarrow{H_3O^+} RCHO$
$(b)$ Formation of aldehyde by reduction reaction of nitrile compounds with $DIBAL-H$ followed by hydrolysis:
Nitriles are selectively reduced by diisobutylaluminium hydride $(DIBAL-H)$ to imines,followed by hydrolysis to aldehydes:
$RC \equiv N \xrightarrow[(ii) H_2O]{(i) AlH(i-Bu)_2} RCHO$
$(c)$ Preparation of ketones from nitrile compounds:
Ketones are prepared by the reaction of nitriles with Grignard reagents $(R'MgX)$ followed by hydrolysis.
$RCN + R'MgX$ $\rightarrow R-C(R')=NMgX$ $\xrightarrow{H_3O^+} R-C(=O)R' + NH_3 + Mg(OH)X$