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

Abstract

Several K-benzoyl-K-phenylhydroxylamine derivatives were synthesized. Their acid dissociation constants, pK_a, were determined spectrophotometrically. There was a linear relationship between the constants and Hammett′s σ_m values. Furthermore the distribution constants, K_DL, of their reagents between the aqueous and chloroform phases were determined. It was found that both the extraction constants, K_ex, of their copper complexes and the pH values at half extraction, pH_1/2, are practically constant although the pK_a values decrease because of the electron-withdrawing nature of the substituted group. It cdn be assumed that the values of logK_DC, (where K_DC is the distribution constant of the copper complex) are nearly equal to the values of 2 log K_DL, since the values of log K_DC and log K_DL are proportional to molecular volume on the basis of the regular solution theory; that is, a relationship between K_DC and K_DL can be expressed as follows; logK_DC=2logK_DL+constant. Since the values of K_ex and K_DC K_DL^-2 for each of the chelates can be regarded as constant, an analogous relationship between K_a and β₂ can also be derived as follows: logβ₂=2pK_a+constant.