Covalent Additions of Glutathione, Cysteine, Homocysteine, Cysteamine and Thioglycolic Acid to Quinazoline Cation

Abstract

A linear relationship with a gradient of 0·38 was found to exist between the γ values of thiols and the pK_a values of their mercapto groups. The γ value of a nucleophilic reagent is a relative measure of the extent to which it will covalently add across >C=N-,>C=O and >C=C< groups, γ values for the thiols were calculated from the equilibrium constants for their covalent addition to quinazoline cation at 25º, l 0.1 M. The results indicate that substituents in a thiol influence both the pK_a value of the mercapto group and the γ value in a similar manner but they have a significantly greater effect on the pK_a value.