GAS-SOLID CHROMATOGRAPHIC STUDIES OF CYCLIC HYDROCARBONS ON SALT-MODIFIED ALUMINAS AND POROUS SILICA BEADS

The differential enthalpies, entropies, and free energies of adsorption for a series of cyclic C8, C7, C6, and C5 alkenes, polyalkenes, and alkanes on salt-modified porous silica beads and aluminas have been determined using elution gas chromatography. The results established that the degree of specific interaction by the pi-electron systems is highly dependent on geometric and steric factors. This permits gas-solid chromatography to be used as an effective tool for the determination of molecular structures of cyclic unsaturated hydrocarbons. The data confirm that 1,3,5,7-cyclooctatetraene and 1,3,5-cycloheptatriene are both in the tub configuration when adsorbed, and that conjugated cyclic dienes cannot interact as effectively as the nonconjugated isomers capable of having the two pi bonds in a plane. © 1968, American Chemical Society. All rights reserved.