Question

Which of the following reactions are suitable for the preparation of primary amines?

• A. Action of ammonia on alkyl halides
• B. Hofmann rearrangement
• C. Gabriel synthesis
• D. Hydrogenation of isocyanides

Answer 1

Answer: (B), (C)

Gabriel synthesis

(a) Action of $N{H}_3$ on $R-X$ will lead to formation of mixture of product including $1^o,2^o,3^o$ and quaternery amines.

(b) Hoffmann bromamide reaction produces primary amines.
$R-\stackrel{O}{\stackrel{||}{C}}-N{H}_2\underset{KOH}{\overset{B{r}_2}{\to }}\underset{\left(1^o\text{amine}\right)}{R-N{H}_2}$

(c) Gabriel's phthalimide synthesis is used for the preparation of primary amines.

(d) $R-NC\stackrel{H_2/Pt}{\to }\underset{\left(2^o\text{amine}\right)}{R-NH-C{H}_3}$