Question

Question: Draw a stepwise, detailed mechanism for the following intramolecular reaction that forms a cyclic ether.

Short answer

Answer

Step-by-step solution

Step-by-Step SolutionStep 1: Formation of cyclic ethers

Cyclic ethers will be formed from intramolecular ${\mathbf{S}}_{\mathbf{N}}\mathbf{2}$ (bimolecular substitution) reactions that occur between two -OH groups

The mechanism of the given reaction

The conjugate acid of the $-\mathrm{OH}$is the best leaving group. On reaction with an acid, the$-\mathrm{OH}$becomes$\stackrel{+}{\mathrm{O}}{\mathrm{H}}_2$, and it leaves the substrate molecule and forms a $3°\left(\mathrm{tertiary}\right)$carbocation intermediate.

Then, the other $-\mathrm{OH}$acts as a nucleophile, and it forms a bond with the $3°\left(\mathrm{tertiary}\right)$carbocation, and thus, the product cyclic ether is formed.

Formation of cyclic ether