Study of the palmitic-choleic acid by vapour pressure measurements and Van Der Waals' energy calculations

Vaporization studies in pure palmitic acid (CH3(CH2)14COOH; hereafter referred to as PAL) and the PAL-choleic acid (DCAPAL) were accomplished by resorting to the torsion effusion method. The vapour pressure in equilibrium with the condensed phase was determined for PAL as. log P (kPa) = (9.77 ± 0.16) - (4677 ± 62)/T and for DCAPAL as. log P (kPa) = (25.28 ± 0.56) - (12355 ± 224)/T. By the second-law treatment of the vapour pressure data, ?H0379 = 89 ± 2 and ?H0445 = 237 ± 5 kJ mol-1 were derived for PAL vaporization from the pure compound and from DCAPAL, respectively. Moreover, van der Waals' energy calculations were performed on DCAPAL to obtain an empirical correlation between the host-guest interaction energy and the enthalpy change associated with the release of PAL from the crystal of DCAPAL.