Oxime

An oxime is a chemical compound belonging to the imines, with the general formula R¹R²C=N O H, where R¹ is an organic side-chain and R² may be hydrogen, forming an aldoxime, or another organic group, forming a ketoxime. O-substituted oximes form a closely related family of compounds. Amidoximes are oximes of amides with general structure RC(=NOH)(NRR').

Oximes are usually generated by the reaction of hydroxylamine and aldehydes or ketones. The term oxime dates back to the 19th century, a combination of the words oxygen and imine.

Structure and properties

Oximes exist as two geometric stereoisomers: a syn isomer and an anti isomer. Aldoximes, except for aromatic aldoximes, which exist only as anti isomers, and ketoximes can be separated almost completely and obtained as a syn isomer and an anti isomer.

Oximes have three characteristic bands in the infrared spectrum, at wavenumbers 3600 (O-H), 1665 (C=N) and 945 (N-O).

In aqueous solution, aliphatic oximes are 10²- to 10³-fold more resistant to hydrolysis than analogous hydrazones.