Solvent Extraction of Copper with N-Benzoyl-N-phenylhydroxylamine Derivatives

Abstract

Several K-benzoyl-K-phenylhydroxylamine derivatives were synthesized. Their acid dissociation constants, pKa, were determined spectrophotometrically. There was a linear relationship between the constants and Hammett′s σm values. Furthermore the distribution constants, KDL, of their reagents between the aqueous and chloroform phases were determined. It was found that both the extraction constants, Kex, of their copper complexes and the pH values at half extraction, pH1/2, are practically constant although the pKa values decrease because of the electron-withdrawing nature of the substituted group. It cdn be assumed that the values of logKDC, (where KDC is the distribution constant of the copper complex) are nearly equal to the values of 2 log KDL, since the values of log KDC and log KDL are proportional to molecular volume on the basis of the regular solution theory; that is, a relationship between KDC and KDL can be expressed as follows; logKDC=2logKDL+constant. Since the values of Kex and KDC KDL-2 for each of the chelates can be regarded as constant, an analogous relationship between Ka and β2 can also be derived as follows: logβ2=2pKa+constant.