In organic chemistry, an ortho ester is a functional group containing three alkoxy groups attached to one carbon atom, i.e. with the general formula . Orthoesters may be considered as products of exhaustive alkylation of unstable orthocarboxylic acids and it is from these that the name ortho ester is derived. An example is ethyl orthoacetate, , more correctly known as 1,1,1-triethoxyethane.