High level ab initio calculations show that the S(N)2 reaction of the cyanide ion with ethyl chloride is catalysed by 1,4-benzenedimethanol in dipolar aprotic solvents through selective two hydrogen bonds. In apolar solvents, combined with phase transfer catalysis, the 1,4-benzenedimethanol could replace some water molecules hydrating the cyanide ion and induce a substantial rate acceleration effect. (c) 2006 Elsevier B.V. All rights reserved.