b
\(\,\,R\, - \,\,CN\,\,\xrightarrow{{\operatorname{Re} duction}}\,\mathop {R\, - \,C{H_2}N{H_2}}\limits_{{1^o }\,Amine}\)                \((a)\)

\(R{\mkern 1mu}  - {\mkern 1mu} {\mkern 1mu} CN{\mkern 1mu} \xrightarrow{{(1){\kern 1pt} C{H_3}MgBr}}{\mkern 1mu} \) \(R{\mkern 1mu}  - {\mkern 1mu} \mathop {{\text{ }}C}\limits_{\mathop {{\text{ }}|\,}\limits_{\,\,\,\,\,\,C{H_3}} } {\mkern 1mu} {\mkern 1mu}  = {\mkern 1mu} {\mkern 1mu} N{\mkern 1mu}  - {\mkern 1mu} {\mkern 1mu} MgBr{\mkern 1mu} \) \(\xrightarrow{{{H_2}O}}{\mkern 1mu} R{\mkern 1mu}  - {\mkern 1mu} \mathop {{\text{ }}C}\limits_{\mathop {\mathop {{\text{ }}|}\limits_{\,\,\,\,\,\,\,C{H_3}} }\limits_{Ketone} } {\mkern 1mu}  = {\mkern 1mu} {\mkern 1mu} O\)                \((b)\)

\(\,R\, - \,NC\,\xrightarrow{{Hydrolysis}}\,\mathop {R\, - \,N{H_2}}\limits_{{1^o }Amine}\)          \((c)\)

\( \,R - N{H_2}\,\xrightarrow{{HN{O_2}}}\,\mathop {R - OH}\limits_{Alcohol}\)        \((d)\)