Question

Give an example for each describe the following reactions. Hoffmanns bromamide reaction.

Answer 1

Hoffmann's bromamide reaction:-

1. In this reaction the Acid amides $(\mathrm{R}-\mathrm{CO}-{\mathrm{NH}}_2)$ is reacted with ${\mathrm{Br}}_2$in presence of a base ($\mathrm{NaOH}$ or $\mathrm{KOH}$) at around $70°\mathrm{C}$ to yield primary amines.
2. The amines formed has one Carbon atom less than the parent acid amide, hence it is called a step-down reaction.
3. This reaction also occurs in the presence of Sodium hypobromite $\left(\mathrm{NaOBr}\right)$or Potassium hypobromite $\left(\mathrm{KOBr}\right)$
4. The general reaction is:

$\underset{\mathrm{Acid}\mathrm{amides}}{\mathrm{R}-{\mathrm{CONH}}_2}\underset{70°\mathrm{C}}{\overset{{\mathrm{Br}}_2/\mathrm{KOH}\mathrm{or}\mathrm{KOBr}/\mathrm{KOH}}{\to }}\underset{\mathrm{Primary}\mathrm{amines}}{\mathrm{R}-{\mathrm{NH}}_2}$

Example of Hoffmann bromamide reaction:-

1. When Acetamide${\mathrm{CH}}_3-{\mathrm{CONH}}_2$ is reacted with is reacted within${\mathrm{Br}}_2$in presence of a base ($\mathrm{NaOH}$ or $\mathrm{KOH}$) at around $70°\mathrm{C}$ it produces Methylamine${\mathrm{CH}}_3-{\mathrm{NH}}_2$.
2. The Methylamine produced has 1 carbon atom less than Acetamide.
3. The complete reaction is as follows:

$\underset{\mathrm{Acetamide}}{{\mathrm{CH}}_3-{\mathrm{CONH}}_2}\underset{70°\mathrm{C}}{\overset{{\mathrm{Br}}_2/\mathrm{KOH}\mathrm{or}\mathrm{KOBr}/\mathrm{KOH}}{\to }}\underset{\mathrm{Methylamine}}{{\mathrm{CH}}_3-{\mathrm{NH}}_2}+\underset{\mathrm{Potassium}\mathrm{bromide}}{2\mathrm{KBr}}+\underset{\mathrm{Potassium}\mathrm{carbonate}}{{\mathrm{K}}_2{\mathrm{CO}}_3}+\underset{\mathrm{Water}}{2{\mathrm{H}}_2\mathrm{O}}$