Title of article
Quantum mechanics investigation of acid dissociation constant of carboxylic acids in aqueous solution
Author/Authors
Khaleghian, M Department of Chemistry - Eslamshahr Branch - Islamic Azad University, Tehran , Ghashami, Gh. R Department of Engineering - Eslamshahr Branch - Islamic Azad University, Tehran
Pages
6
From page
1
To page
6
Abstract
According to the Bronsted definition, any compound which has a hydrogen atom is an acid, since it
may be lost as a proton. A thermodynamical cycle is proposed to calculate absolute pKa values for
Bronsted acids in aqueous solution. The equilibrium of dissociation of a Bronsted acid depends on
the interaction of the acid and its conjugate base with solvent molecules. There fore the pKa value
depends on the solvent medium. The polarizable continuum model (PCM) was used to describe the
solvent, and absolute pKa values were computed for different compounds: HCOOH, CH3COOH,
C6H5COOH, FCH2COOH and CH3CH2COOH. The model of furnishes pKa values was in good
agreement with the experimental results for some classes of compounds. The quantum Mechanics
(QM) calculations were carried out with the GAUSSIAN 98 program based on HF/6-31+G** level.
Keywords
pKa , Acid dissociation constants , Free energy , Gas phase , Solution , Thermodynamic cycles , Deprotonation
Journal title
Astroparticle Physics
Serial Year
2012
Record number
2438968
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