Effect of dielectric constant on protonation equilibria of 2, 3-dihydroxybenzoic acid and malonic acid in 1, 2-propanediol-water mixtures

Autor:	Belete Yilma Hirpaye, Gollapalli Nageswara Rao, Mekonen Tirfu Zekarias
Rok vydání:	2012
Předmět:	Chemical Health and Safety Chemical models Health Toxicology and Mutagenesis 2 3-Dihydroxybenzoic acid Protonation Dielectric Malonic acid Toxicology Propanediol chemistry.chemical_compound chemistry Ionic strength Organic chemistry Physical chemistry
Zdroj:	Chemical Speciation & Bioavailability. 24:253-260
ISSN:	2047-6523 0954-2299
DOI:	10.3184/095422912x13488329001304
Popis:	The protonation constants of 2,3-diydroxybenzoic acid (2, 3-DHBA) and malonic acid (MA) at 303.0 ± 0.1 K and 0.16 mol L-1 ionic strength in various concentrations (0–60% v/v) of 1,2-propanediol–water-mixtures were determined by pH-metric method. The protonation constants were calculated with MINIQUAD75 computer program. Selection of the best fit chemical models of the acid–base equilibria was based on statistical parameters. The log K values were found to increase with the increase in percentage of 1,2-propanediol and vary linearly with the reciprocal of the dielectric constant of the medium. This has been attributed to the dominance of electrostatic forces. Distributions of species and effect of influential parameters on the protonation constants are also presented.
Databáze:	OpenAIRE
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