Carboxylic Acid-N Base Hydrogen Bonds with Large Proton Polarizability in Acetonitrile as a Function of the Basicity of the Hydrogen Bond Acceptors
Open Access
- 1 October 1984
- journal article
- Published by Walter de Gruyter GmbH in Zeitschrift für Naturforschung A
- Vol. 39 (10) , 986-992
- https://doi.org/10.1515/zna-1984-1013
Abstract
Carboxylic acid-N base systems are studied in acetonitrile. The association equilibrium constants Ka and the proton transfer equilibrium constants KPT in the OH···N ⇄ O-···H+N bonds formed, are determined from IR spectra. The association constants Ka increase in proportion to the basicity of the hydrogen bond acceptors. The same is true with regard to the proton transfer constants. The OH ···N ⇄ O- ···H+N equilibria are shifted with increasing basicity to the right hand side. It is discussed that this shift is caused by an intrinsic effect as well as by an extrinsic one (interaction of the dipole of the hydrogen bond with its environment). A linear relation exists between log KPT and ⊿pKa (pKa of the protonated base minus pKa of the acid). 50% transfer of the protons to the N base is found at ⊿pKa = 2.6. As indicated by intense continua. these hydrogen bonds show large proton polarizability if the degree of asymmetry of their proton potentials is not too large.Keywords
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