In chemistry, the alkoxy group is an alkyl (carbon and hydrogen chain) group singularly bonded to oxygen; thus R–O. The range of alkoxy group is vast, the simplest being methoxy (CH3O–). An ethoxy group (CH3CH2O–) is found in the organic compound ethyl phenyl ether, C6H5OCH2CH3 which is also known as ethoxybenzene. Related to alkoxy groups are aryloxy groups, which have an aryl group singular bonded to oxygen such as the phenoxy group (C6H5O–).
An alkoxy or aryloxy group bonded to an alkyl or aryl (R1–O–R2) is an ether. If bonded to H it is an alcohol. An alkoxide (RO–) is the ionic or salt form; it is a derivative of an alcohol where the proton has been replaced by a metal, typically sodium.