Novel cyanohydrin derivatives of general formula (I) wherein R.sup.1 is hydrogen, alkyl, alkoxy, perfluoroalkyl or perfluoroalkoxy, R.sup.2 is alkyl, r is 1 to 10, n and m are 0 or 1, provided if both n and m are 0 then X is (II) or (III), where (F) indicates one or more optional fluorines, p is 0 or 1, Z is a single bond if p is 0 and COO if p is 1; and if one or both of n or m are 1 then X is (IV), where each ring A, B and C is phenyl, fluoro- or chloro-phenyl, cyclohexyl, pyrimidyl, pyridyl, or dioxanyl, A, B and C are single bonds or linking groups, and (a+b+c) is 2 or 3. Liquid crystal materials containing these compounds are also described.