GAS-CHROMATOGRAPHIC DETERMINATION OF VAPOR-PRESSURES OF PHEROMONE-LIKE COMPOUNDS .4. ACETATES, A REINVESTIGATION

The equilibrium vapour pressures P and enthalpies of vaporization Delt a H for an acetate series with carbon numbers varying from 10 to 18 we re determined using a GC technique. The P and Delta H quantities at 29 8.15 K were calculated for more than 100 (un)saturated linear-chain co mpounds based on the experimental retention time measurements of the t est acetates and five reference alkane standards with known vapour pre ssures. The advantage of utilizing several standards in the GC based v apour pressure determinations was demonstrated by comparison with prev iously published data. Additionally, empirical equations were develope d for correlating In P and Delta H with the number of carbon atoms (N) and double bond positions (Delta) in the chain. It was shown that wit h these two-parameter equations the vapour pressures of acetates can b e predicted with a considerable degree of confidence. In the case of E 2-, E3- and Z4-alkenyl acetate isomers, however, anomalies in retentio n time/vapour pressure-structure relationships were observed, indicati ng specific types of polar interactions.