A compound having ferroelectric liquid crystal properties of the formula: ##STR1## wherein A is the residue of a liquid crystal material or a liquid crystal compatible material; X is O or S; n is 0 or 1; Y is any inert group which does not cause the melting point of the compound of Formula I to exceed 200.degree. C.; R.sup.1 is selected from H, C.sub.1-4 -alkyl and halogen; and R.sup.2 is C.sub.1-4 -alkyl or halogen; provided that R.sup.1 and R.sup.2 are different. In a suitable environment the compound is capable of alignment in two metastable states and is therefore suitable for use in multiplex-addressed, liquid crystal devices, such as flat bed large area screens and displays.