Illustrated Glossary of Organic Chemistry

Ethoxide (ethoxide ion; EtO-): CH3CH2O-; the conjugate base of ethanol. A strong base (frequently used in E2 and enolate reactions) and a good nucleophile.

Structure of ethoxide ion.


Internal trisubstituted alkene
Major product

Terminal disubstituted alkene
Minor product
Sodium ethoxide as a base in an E2 reaction, illustrating Zaitsev's rule.

Potassium ethoxide as a nucleophile in a Williamson ether synthesis (an SN2 reaction).