The invention relates to the use of metal cation-exchangeable layered clays in organic reactions catalysed by protons in which water is not a stoichiometric reactant. Such organic reactions include the reaction of an olefin with a carboxylic acid in the liquid or vapour phase to produce an ester, e.g. reaction of ethylene with acetic acid to produce ethyl acetate, reaction of an alkanol with a linear olefin at temperatures above 100°C to produce an ether, the conversion of primary or secondary aliphatic alcohols or polyols into ethers, the conversion of primary or secondary amines into secondary and tertiary amines respectively and the reaction of an olefin with benzene to produce an alkyl benzene.