Question

The given reaction is a :

• A. 1,4 addition reaction
• B. 2,3 addition reaction
• C. Neutralisation reaction
• D. none

Answer 1

The correct option is A 1,4 addition reaction

The given reaction is a 1,4 addition reaction.
In the first step, a molecule of $HBr$ is added to a conjugated diene. Both $H$ atom and $Br$ atom are added to terminal $C$ atoms. This is 1,4 addition or conjugate addition. In the next step, the reaction with $Mg$ in presence of ether gives a Grignard reagent ($R-MgX$) which then attacks a molecule of carbon dioxide. Acid hydrolysis gives carboxylic acid.