9.2.2 Hunsdiecker Reaction
Treatment of aqueous solution of silver oxide with carboxylic acid gives silver salt of carboxylic acid which reacts with Br2 to give a bromo-compound with elimination of CO2 .
Mechanism
The reaction involves the formation of acyl hypobromite and its homolytic cleavage to give acyloxy radical which loses CO2 and the resulting radical reacts with bromine radical or abstracts bromine from a second molecule of the hypobromite.
Mercury(II) and lead(IV) compounds are also known to react similarly. For example, cyclopropanecarboxylic acid with HgO and Br2 affords bromocyclopropane in 45% yield.
Examples:
