Question

Alcohols can be converted to alkyl bromides using PBry​, which couses a complete inversion of stereochemistry. Draw the stepwise mechanism for bromination of an alcohol, Be sure to include non-zero formal charges and lone pairs as necessary.

Answer 1

The bromination of an alcohol involves the SN2 mechanism, where the alcohol is protonated, bromide ion attacks, and the product is an alkyl bromide with an inversion of stereochemistry.

Step-by-step explanation:

The bromination of an alcohol to produce an alkyl bromide involves a substitution reaction with complete inversion of stereochemistry. The mechanism for this transformation is the SN2 mechanism. During this process, the alcohol is first converted into a better leaving group through protonation. Then, a nucleophilic bromide ion attacks the carbon atom bearing the leaving group, resulting in the departure of the water molecule and formation of the alkyl halide product.

The steps involved in this reaction typically include:

1. Protonation of the alcohol oxygen by a strong acid such as HBr, turning the hydroxyl group into a water molecule, a better leaving group.
2. The nucleophilic Br- ion attacks the carbon atom from the opposite side of the leaving group, leading to the formation of a transition state where the carbon atom is pentacoordinate.
3. The departure of the water molecule and completion of the nucleophilic attack, resulting in the formation of the alkyl bromide with an inverted stereochemistry at the carbon center.