Epoxides can also undergo ring opening when react with nucleophiles such as an alkoxide ion or hydroxide ion (Scheme 21). In case of unsymmetrical epoxide, the alkoxide ion attacks primarily at the less substituted carbon atom via S_N2 like reaction.

Scheme 21

Like other nucleophiles, Grignard and organolithium reagents attack epoxides to give alcohols (Scheme 22). These nucleophiles usually attack the less hindered epoxide carbon atom. Organolithium reagents are more selective than Grignard reagents in attacking the less hindered epoxide carbon atom. Grignard reagents may give mixtures of products unless one of the carbons atom is strongly hindered.

Scheme 22

Polyether is formed when we treat ethylene oxide with sodium methoxide (Scheme 23). The alkoxide group at the end of the chain is protonated by methanol.