The ratio-of cis-to trails-olefin obtained in base catalysed bimolecular elimination from 5- nonyl bromide, 5-nonyltrimethylammonium and 5-nonyldimethylsulphonium ions has been found to vary greatly in dependence on the base and solvent employed. In the case of the bromide the proportion of the cis-to the trans-olefin increases on going from methoxide- methanol to ethoxide-ethanol and tert. butoxide-tert. butanol but the opposite trend was ...