Question

Which of the following method(s) does work for the preparation of secondary amine?

• A. $R_{3}N\underset{\begin{array}{c}\left(ii\right)H_3{O}^{+}\\ \left(iii\right)\Delta \end{array}}{\overset{\left(i\right)Br-CN}{\to }}?$
• B. $R-\stackrel{O}{\stackrel{||}{C}}-NH-R^{\prime }\stackrel{LiAl{H}_2}{\to }?$
• C. $RNC\underset{\Delta }{\overset{Nl/H_2}{\to }}?$
• D. All of these

Answer 1

The correct option is D All of these

(A) Tertiary amines react with cyanogen bromide to form a dialkylcyanamide which, on hydrolysis, gives a secondary amine.

$R_{3}N+BrCN\to [R_{3}NCN{]}^{+}B{r}^{-}\to RBr+R_{2}NCN\stackrel{H^{+}}{\to }{R}_{2}NH$

(B) Secondary amides $\left(RCONHR\right)$ react with lithium aluminium hydride (LiAlH4) to form secondary amines $\left(RC{H}_{2}NH{R}^{\prime }\right)$

$R\stackrel{\stackrel{O}{||}}{C}NHR+H-A{l}^{-}{H}_3\to R\stackrel{\stackrel{O^{-}}{|}}{C}=NR\to RC{H}_{2}NHR$

(C) Secondary amines are produced by the reduction of isocynaide.

$RNC\stackrel{Ni/H_2}{\to }RNHC{H}_3$