Comparative QSAR of the sulfonamide function.

The aromatic SO(2)NH(2) function has been characterized in biological reactions and in physical organic chemical reactions using the Hammett constant sigma, the Swain-Lupton parameter F and steric constants. The results allow comparable support for the biological processes from the much better understood mechanistic organic reactions. The approach is applied to the enzyme carbonic anhydrase and the rate of excretion of Na(+) by rats. From the study of QSAR on the ionization of the amide function, it is clearly apparent that it is the ionized form of SO(2)NH(2) that promotes the biological processes. It is clear from Fujita-Nishioka proposal that, in dealing with ortho substituents, one should routinely test sigma, F and a steric parameter to account for substituent effects.