Article

Prof. G. Nageswara Rao, Department of Inorganic Chemistry, School of Chemistry, Andhra University, Vishakapatnam.; Dr. S. Raju ,School of Chemistry, Andhra University, Vishakapatnam.; Dr. K. B. K. Naik ,School of Chemistry, Andhra University, Vishakapatnam.; Dr. B. Ananda Kumar ,School of Chemistry, Andhra University, Vishakapatnam.

Effect of DMSO on the protonation equilibria of L-Glutamic acid and L-Histidine have been studied in varying concentrations (0-60% v/v) of DMSO–water mixtures maintaining an ionic strength of 0.16 mol/l at 303 K using pH metric method. The protonation constants have been calculated with the computer program MINIQUAD75 and the best fit models are arrived at based on statistical grounds employing crystallographic R factor, χ2, skewness and kurtosis. The variation of protonation constants with dielectric constant of the medium is attributed to the electrostatic and non-electrostatic forces. The effect of errors on the protonation constants has also been presented.