Question

What is produced when ${\mathrm{CH}}_3{\mathrm{CONH}}_2$ reacts with $\mathrm{NaOBr}$? Is $\mathrm{NaOBr}$ a product of (or equivalent to) ${\mathrm{Br}}_2+\mathrm{NaOH}$ which are used in the Hoffmann bromamide degradation reaction?

Answer 1

Hoffmann bromamide degradation reaction:

• Hoffmann bromamide reaction mechanism generally includes the use of alkali as a strong base to attack the amide, leading to the deprotonation and the subsequent generation of an anion.
• This reaction is used for the conversion of a primary amide to a primary amine with one less carbon atom.
• This is accomplished by heating the primary amide with a mixture of a halogen (chlorine or bromine), a strong base, and water.

The reaction of ${\mathrm{CH}}_3{\mathrm{CONH}}_2$ with $\mathrm{NaOBr}$:

• The reagent that is required for the Hoffman degradation reaction is a combination of Bromine and aqueous Sodium hydroxide $(\mathrm{B}{\mathrm{r}}_2+\mathrm{NaOH})$.
• The hydroxide ion, being basic in nature, abstracts a proton attached to the nitrogen atom of the amide group and it gets substituted by a bromine atom.
• The chemical reaction can be depicted as:
  ${\mathrm{CH}}_3{\mathrm{CONH}}_2+{\mathrm{Br}}_2+4\mathrm{NaOH}\to {\mathrm{CH}}_3{\mathrm{NH}}_2+{\mathrm{Na}}_2{\mathrm{CO}}_3+2\mathrm{NaBr}+2{\mathrm{H}}_2\mathrm{O}$
• In an aqueous medium, the bromine-bromine bond of the atomic molecule is also polarized to some extent that it gets cleaved by the action of sodium hydroxide base resulting in the formation of Sodium hypobromite $\left(\mathrm{NaOBr}\right)$.
• Therefore, $\mathrm{NaOBr}$ is a reagent for Hoffmann bromamide degradation that is prepared in situ by the reaction between bromine and aqueous sodium hydroxide.
• The chemical reaction can be depicted as:
  ${\mathrm{Br}}_2+2\mathrm{NaOH}\to \mathrm{NaBr}+\mathrm{NaOBr}+{\mathrm{H}}_2\mathrm{O}$
• Thus, the product of the reaction between ${\mathrm{CH}}_3{\mathrm{CONH}}_2$and $\mathrm{NaOBr}$ is methenamine$$C{H}_{3}N{H}_2$$. Yes, $\mathrm{NaOBr}$ is a product of $(\mathrm{B}{\mathrm{r}}_2+\mathrm{NaOH})$ and is a reagent equivalent to the combination of bromine and aqueous sodium hydroxide.