Enthalpies of Solution and Excess Enthalpies of Oxo Compounds by ...

Published: Journal of Chromatographic Science, Volume 37, Number 1, January 1999, pp. 11-16.

Enthalpies of Solution and Excess Enthalpies of Oxo Compounds by Capillary Gas Chromatography
Miklós Görgényi and Károly Héberger

The temperature dependence of retention data is measured for5 n-alkanes and 35 aliphatic ketones and aldehydes on capillary columns using 4 bonded stationary phases: dimethyl polysiloxane (HP-1), phenyl methyl polysiloxane (HP-50), trifluoropropyl methyl polysiloxane (DB-210), and polyethylene glycol (HP-Innowax). A novel equation is deduced from the expressions describing the thermodynamic relations of the specific retention volume. The enthalpy of solution, ÆsolH°, is determined from the fits of ln (k/T) versus 1/T, where k is the retention factor and T is the column temperature. The excess enthalpy HE is determined from the enthalpy of vaporization in the middle of the temperature range (the enthalpy of vaporization is available from the literature) and from ÆsolH°. The ÆsolH° values of the n-alkanes decrease with increasing column polarity on the McReynolds scale, whereas those of the alkanals and ketones tend to increase. The values of HE show that, with increasing polarity of the stationary phase, the stronger interaction with the C=O group is cancelled out by a similar decrease in interaction with the apolar part of the solute. With increasing molecular size of the n-alkanals, the solute–stationary phase interaction is increasingly less able to compensate the energy necessary for hole formation in the stationary phase.

Reproduction of editorial content of this journal is prohibited without publisher’s permission.

This article is available in its entirety by fax for $40.00.
Visa, MasterCard & Amex accepted.

To order electronically click here
or call: 847-647-2900 ext. 1323
or fax request to: 847-647-1155.

To order multiple copies click here.

Please indicate JCS volume and issue along with page numbers.