Dissociation constants of weak organic acids in protic solvents obtained from their first hyperpolarizabilities in solution

Ray, Paresh Chandra and Das, Puspendu Kumar (1995) Dissociation constants of weak organic acids in protic solvents obtained from their first hyperpolarizabilities in solution. In: Journal of Physical Chemistry, 99 (51). pp. 17891-17895.

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Abstract

The first hyperpolarizabilities (beta) of some weak aromatic organic acids have been measured in protic solvents by the hyper-Rayleigh scattering (HRS) technique at low concentrations. The measured hyperpolarizability (beta(m)) varies between the two extreme limits: the hyperpolarizability of the acid form (beta(HA)) at the lower side and that of the basic form (beta(A-)) at the higher side. The degree of dissociation (alpha) of the acid in a solvent is related to the measured hyperpolarizability, beta(m), by the following relationship: beta(m)(2)=(1-alpha)beta(HA)(2)+alpha beta(A-)(2). The calculated beta's including solvent effects in terms of an Onsager field do not reproduce the experimentally measured hyperpolarizabilities. Other solvent-induced effects like hydrogen bonding and van der Waals interactions seem to influence the first hyperpolarizability and, thus, indirectly the extent of dissociation of these weak acids in these protic solvents.

Item Type:	Journal Article
Publication:	Journal of Physical Chemistry
Publisher:	American Chemical Society
Additional Information:	Copyright of this article belongs to American Chemical Society.
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	27 May 2011 10:34
Last Modified:	27 May 2011 10:34
URI:	http://eprints.iisc.ac.in/id/eprint/38002

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