Spectrophotometric pKa Values of 3-(m-Nitrophenyl)-1,5-Diphenyl Formazan (MNF) and 3-(p-Nitrophenyl)-1,5-Diphenyl Formazan (PNF) in Different MeCN-Water Binary Mixtures
Abstract
The acid dissociation constants of 3-(m-nitrophenyl)-1,5-diphenyl formazan (MNF) and 3-(p-nitrophenyl)-1,5-diphenyl formazan (PNF) have been determined in acetonitrile-water binary mixtures [50%, 60% and 70% (v/v)] by spectrophotometric method at 25 degrees C and an ionic strength of 0.1 mol .L-1 KCl. The absorption spectra were recorded in solutions of varying pH-values. Data evaluation was performed using the STAR software program which calculates stability constants and molar absorbances of the pure species by multilinear regression. A linear relationship between acidity constants and the mole fraction of acetonitrile in the solvent mixture was observed. The effect of solvent properties on acid-base behavior was discussed. The effect of nitro groups attached to para and meta positions on the ionization constant were investigated and the results were recorded.
Source
JOURNAL OF THE CHEMICAL SOCIETY OF PAKISTANVolume
34Issue
5Collections
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