Question

Show the products of the reactions of these carboxylic acids with ${\mathbf{PBr}}_{\mathbf{3}}\mathbf{/}{\mathbf{Br}}_{\mathbf{2}}$before and after hydrolysis.

1. pentanoic acid
2. phenylacetic acid
3. succinic acid
4. oxalic acid

Short answer

In alpha bromination reaction, a hydrogen atom is replaced with a bromine atom on the alpha carbon of a carboxylic acid.

The product formed from alpha bromination reaction is alpha -bromoacids which are importantly used as synthetic intermediates in various chemical reactions.

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Step-by-step solution

Alpha Bromination of acid

In alpha bromination reaction, a hydrogen atom is replaced with a bromine atom on the alpha carbon of a carboxylic acid.

The product formed from alpha bromination reaction is alpha -bromoacids which are importantly used as synthetic intermediates in various chemical reactions.

Alpha bromination of pentanoic acid

On reacting with bromine (Br₂) and phosphorous tribromide (PBr₃), Pentanoic acid forms 2-bromo pentanoylbromide, which on hydrolysis forms alpha-bromoacid known as 2-bromopentanoic acid.

Formation of 2-bromopentanoic acid

Alpha bromination of phenylacetic acid

On reacting with bromine (Br₂) and phosphorous tribromide (PBr₃), phenylacetic acid forms 2-bromo-2-phenyl acetyl bromide, which on hydrolysis forms alpha-bromoacid known as 2-bromo-2-phenylacetic acid.

Formation of 2-bromo-2-phenylaceticacid

Alpha bromination of succinic acid

On reacting with bromine (Br₂) and phosphorous tribromide (PBr₃), succinic acid forms 3,4-dibromo-4-oxobutanoic acid, which on hydrolysis forms alpha-bromoacid known as 2-bromosuccinic acid.

Formation of 2-bromosuccinic acid

Alpha bromination of oxalic acid

On reacting with bromine (Br₂) and phosphorous tribromide (PBr₃), oxalic acid forms 2-bromo-2-oxoacetic acid , which on hydrolysis does not forms alpha-bromoacid as there is no alpha hydrogen present in the 2-bromo-2-oxoacetic acid.

No product is formed