Question

${\mathrm{CH}}_3\mathrm{CHO}+{\mathrm{NH}}_2\mathrm{OH}\stackrel{∆}{\to }\mathrm{P}\stackrel{{\mathrm{H}}^{+}}{\to }\mathrm{Q}\stackrel{{\mathrm{Br}}_2/\mathrm{KOH}}{\to }\mathrm{R}({\mathrm{CH}}_3{\mathrm{NH}}_2)$

Identify P and Q

Answer 1

Given reaction is as follows:

${\mathrm{CH}}_3\mathrm{CHO}+{\mathrm{NH}}_2\mathrm{OH}\stackrel{∆}{\to }\mathrm{P}\stackrel{{\mathrm{H}}^{+}}{\to }\mathrm{Q}\stackrel{{\mathrm{Br}}_2/\mathrm{KOH}}{\to }\mathrm{R}({\mathrm{CH}}_3{\mathrm{NH}}_2)$

This is the reaction in which acid induces rearrangement of oxime to give amides.

The rearrangement will take place in the following manner:

$\mathrm{aldoxime}\stackrel{{\mathrm{H}}^{+}}{\to }\mathrm{N}-\mathrm{substituted}\mathrm{amide}$

${\mathrm{CH}}_3\mathrm{CHO}+{\mathrm{NH}}_2\mathrm{OH}\stackrel{∆}{\to }{\mathrm{CH}}_3{\mathrm{C}}^{+}=\mathrm{NH}\stackrel{{\mathrm{H}}^{+}}{\to }{\mathrm{CH}}_3{\mathrm{CONH}}_2$

So, the P is an intermediate carbocation which on reaction with acid becomes N-substituted amide(ethyl amide) which is Q.

${\mathrm{CH}}_3{\mathrm{CONH}}_2\stackrel{{\mathrm{Br}}_2/\mathrm{KOH}}{\to }{\mathrm{CH}}_3{\mathrm{NH}}_2+{\mathrm{K}}_2{\mathrm{CO}}_3+\mathrm{KBr}+{\mathrm{H}}_2\mathrm{O}$

This is known as the Hoffmann bromamide degradation reaction in which amide is converted into amine in a basic medium and one carbon will be degraded from the original amide.