Question

Question: If the reaction of an alcohol with ${\mathbf{PBr}}_{\mathbf{3}}$follows an${\mathbf{S}}_{\mathbf{N}}\mathbf{2}$ mechanism, what is the stereochemistry of the alkyl bromide formed from (R)-butan-2-ol?

Short answer

Answer

The stereochemistry of the alkyl chloride formed from (R)-butan-2-ol is (S)-2-bromobutane.

Step-by-step solution

Step-by-Step Solution Step 1: SN2 reaction

In the ${\mathbf{S}}_{\mathbf{N}}\mathbf{2}$reaction, a single step involves the attacking of the nucleophile and the loss of the leaving group. The inversion of the configuration takes place at the electrophilic carbon center.

Formation of the product

The reaction of (R)-butan-2-ol with ${\mathrm{PBr}}_3$undergoes the ${\mathrm{S}}_{\mathrm{N}}2$ mechanism and forms the inversion of the configuration, which means that (S)-2-bromobutane is formed.

The reaction is shown below.

Formation of alkyl halide