A new developed potentiometric method for the determination of pKa values for syn and anti isomer pair in 3 and 4- hydroxybenzaldoximes

Author(s): A.S.P.Azzouz, D.P.Al-Bakzo

Four syn and anti isomers derived from 4-hydroxybenzaldoxime and 3- hydroxybenzaldoxime were prepared by standard method. Their structures were confirmed by using physical methods, namely UV-IR spectra and melting points. The main object of the study is the determination of pKa values for four isometric oximes by potentiometric method. This method was developed for the first time in studying pKa values for diacidic syn and anti isometric oximes derived from 3 or 4- hydroxybenzaldohyde, or for acidic compounds containing simultaneous oxime and phenol groups. This gives a newdevelopment for potentiometric method over other methods used for pKa determination. Generally the pK1 of phenol and pK2 of oxime groups were found to depend on the type of syn and anti isomer, the temperature and other factors.

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