• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.164-171
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• 2019

The protonation parameters, dissociation constants ($pK_{BH^+}$) of conjugate acid, slope values (m, ${\phi}$ and $m^*$) and correlation coefficients (r) of hydroxamic acids were determined by Hammett acidity function method, Bunnett-Olsen method and excess acidity method in hydrochloric and perchloric acid solutions. Effect of acid concentration on partition and percentage protonation was also studied. $pK_{BH^+}$ values show that hydroxamic acids do not behave as Hammett bases, but hydroxamic acids behave as weak bases in strong acidic solutions. The values of $pK_{BH^+}$ obtained through Bunnett-Olsen method and excess acidity method were compared with the Hammett acidity function. ChemAxon's MarvinSketch 6.1.5 software was also used for determining $pK_a$, pI and microspecies distribution (%) of hydroxamic acids with pH. Hydrogen donor and acceptor values and logD were also obtained. The results show that N-p-chlorophenyl-4-bromobenzohydroxamic acid has the highest $pK_a$ and lowest logD values. On the contrary, N-phenyl-3,5-dinitrobenzohydroxamic acid has lowest the $pK_a$ and highest logD values.