Question

Draw a stepwise mechanism for the following reaction.

Short answer

The mechanism shown for the reaction are given below:-

Step-by-step solution

Type of the reagents used

Strong bases such as hydroxides and ethoxides favor a mixture of both E2 and ${\text{S}}_{\text{N}}\text{2}$ reactions, while bulky bases like sodium or potassium tert-butoxide predominantly favor E2 reactions.

As a weak base and a weak nucleophile ${\mathbf{\text{CH}}}_{\mathbf{3}}\mathbf{\text{OH}}$ are used here, it promotes a mixture of E2 and ${\mathbf{\text{S}}}_{\mathbf{\text{N}}}\mathbf{\text{2}}$.

Mechanism

The reaction proceeds in a ${\text{S}}_{\text{N}}\text{1}$ mechanism, and a positive charge develops on the carbon atom. The lone pair of oxygen attacks the carbon-containing a positive charge and gets attached to that position.

The reaction also proceeds via the E1 mechanism and attacks the terminal hydrogen atom by which the bromine departs from the substrate. A double bond is formed, and hydrogen bromide is obtained as a side product.

Based on the explanations, the mechanism shown for the given reaction are:-

A detailed reaction scheme