The ability of limonene and linalool to rearrange in mesomorphic media is apparently determined by the constraints exerted by the solvent structure on the translational diffusions of the reactant solute molecules. Selective conversions seem to be promoted by the different media. Alkylcyclohexyl- and alkylbicyclohexyl-carboxylic acids and their mixtures with toluic acid have been used as solvents. The B structure of their smectic phases has been demonstrated by X-ray diffraction studies.