Murdoch University Research Repository

Welcome to the Murdoch University Research Repository

The Murdoch University Research Repository is an open access digital collection of research
created by Murdoch University staff, researchers and postgraduate students.

Learn more

Thermochemical parameters and pK a values for chlorinated congeners of thiophenol

Altarawneh, M.ORCID: 0000-0002-2832-3886, Dar, T. and Dlugogorski, B.Z. (2012) Thermochemical parameters and pK a values for chlorinated congeners of thiophenol. Journal of Chemical & Engineering Data, 57 (6). pp. 1834-1842.

Link to Published Version: http://dx.doi.org/10.1021/je3003173
*Subscription may be required

Abstract

Thermochemical parameters of the complete series of congeners of chlorinated thiophenols are derived based on the accurate chemistry model of CBS-QB3. The effect of the change in pattern and degree of chlorination has been thoroughly investigated. Optimized geometries of chlorinated thiophenol molecules exhibit to a large extent very similar geometrical features. Standard enthalpies of formation of chlorinated thiophenol and thiophenoxy radicals are calculated using isodesmic work reactions. Thermodynamic scales of H and G enable the highlighting of the most stable isomer in each homologue group. Standard entropies and heat capacities are calculated with the treatment of internal rotations of the S-H group as hindered rotors. It is found that there is a rather minor effect of changes in pattern and degree of chlorination on the calculated bond dissociation enthalpies (BDH) of the S-H bond in chlorinated thiophenols. Values of solvation energies designate that the interaction of chlorinated congeners of thiophenols with water molecules decreases with the degree of chlorination; however, no apparent dependency can be deduced with regard to the pattern of chlorination. A thermodynamic cycle was constructed to estimate pK a values based on gas phase deprotonation free energies and calculated solvation energies for chlorinated thiophenol molecules and chlorinated thiophenolate anions. Calculated pK a values are in good agreement with limited available experimental measurements.

Item Type: Journal Article
Publisher: American Chemical Society
Copyright: © 2012 American Chemical Society
URI: http://researchrepository.murdoch.edu.au/id/eprint/22655
Item Control Page Item Control Page