Epoxide opening [basic conditions]

Definition

When epoxides are treated with negatively charged nucleophiles, they will add to the least substituted position of epoxide in an S_N2 reaction.

Explanation

Epoxides can be opened under acidic or basic conditions. When an epoxide is subject to attack by a strong nucleophile (such as hydroxide ion) in the first step, the ring opens in an S_N2 process. This nucleophile attacks (back-side attack) an electron-deficient carbon of epoxide, thus cleaving the C-O bond. An alkoxide ion is obtained which then protonated by water in the next step to give the final product with two functional groups on adjacent atoms.