Compounds suitable for use as constituents of ferroelectric smectic liquid crystal compositions, which are esters of formula (I), where R2 and R3 together represent the residue of an alicyclic hydrocarbon ring system where *C is an asymmetric carbon atom and X is a chain of up to three linked aromatic or alicyclic six-membered organic cyclic groups, laterally and/or terminally substituted. Preferred compounds have a formula (II), where R1 is alkyl or alkoxy, A, B, and D are phenyl, fluoro or chloro substituted phenyl or cyclohexyl, n is 0 or 1, Y is a bond or CH2CH2 if n is 0, or a bond CH2CH2COO or COO if n is 1. Preferred groups C(CN)R2R3 are formula (III) and (IV).