STUDIES ON PROTON-LIGAND STABILITY CONSTANTS OF SOME SUBSTITUTED PYRAZOLES, ISOXAZOLES, THIOISOXAZOLES, PYRAZOLINES, ISOXAZOLINES AND THIOISOXAZOLINES pH-METRICALLY AT 0.1 M IONIC STRENGTH

摘要

Proton-ligand stability constants (pK) of 3-(2-hydroxy-3-nitro-5-methyl-phenyl)-1-H-5-phenyl pyrazole (L_1), 3-(2-hydroxy-3-nitro-5-methylphenyl)-5-phenyl isoxazole (L_2), 3-(2-hydroxy-3-nitro-5-methylphenyl)-5-phenyl thioisoxazole (L_3), 3-(2-hydroxy-3-nitro-5-methyl phenyl)-5- (4-methoxyphenyl)-Δ~2-pyrazoline L_4), 3-(2-hydroxy-3-nitro-5-methylphenyl)-5-(4-methoxy- phenyl) isoxazoline (L_5, 3-(2-hydroxy-3-nitro-5-methylphenyl)-5-(4-methoxy-phenyl) thioisoxazoline (L_6) have been investigated pH-meterically in 70% dioxane-water mixture as a solvent. The proton-ligand stability constants for above ligands are found to be more than pH = 8.0. This showed the dissociation of phenolic -OH group. The data obtained were used to determine the standard deviation (σ) by using different values of nA of the same ligand except the difference in concentration of alkali NaOH.