Gel permeation chromatographic separation of stereo-isomers of cyclo- and polycycloalkanes

Methyl derivatives of cyclohexane and several bicyclic and tricyclic saturated hydrocarbons of different stereoisomeric forms were used as model compounds for studying the behaviour of stereoisomers in gel permeation chromatography on a polystyrene gel with a low exclusion limit using tetrahydrofuran as solvent. Differences in elution volumes permit the separation of a number of stereoisomers, the purity of which is greater than 90%. In all of the cases studied, a stereoisomer showing a higher thermodynamic stability and a lower retention index in gas chromatography is eluted from a gel column before a stereoisomer with a higher heat content. In gel permeation chromatography, hydrocarbons with a higher number of stereoisomers were found to have a nearly linear dependence of the elution volume on the relative enthalpy content of stereoisomers calculated by conformational analysis.