Extraction of lead and zinc perchlorates by diantipyrylmethanes and aryl-di-(1-hexyl-5-hydroxy-3-methyl-4-pyrazolyl)methanes

Abstract

The extraction ability of the diantipyrylmethane and aryl-di-(1-hexyl-5-hydroxy-3-methyl-4-pyrazolyl)methane derivatives has been studied by the example of zinc and lead perchlorates extracted into chloroform and dichloroethane. Zinc and lead are extracted from solutions with pH 4.8 and 5.8, respectively, as a [ML2(ClO4)2 complex wherein M = Zn2+; Pb2+, L is the molecule of the reagent. The effective extraction constants were calculated. Diantipyrylmethane exhibits maximal extraction ability. The extraction properties are worsened by the substituents at the methylene atom. In the case of phenyldiantipitylmethane derivatives, a correlation between the values of the extraction constants and the Hammett s constants of the substituents in the phenyl radical is observed. A decrease in the extraction ability of diantipyrylmethane derivatives with introducing of the substituents to the methylene carbon atom is explained by steric factors. In accordance with quantum-chemical calculation, the zinc complex with diantipyrylmethane has a tetrahedral structure but in the case of substituted reagents this structure is flat and less characteristic for zinc atoms. The diantipyrylmethane derivatives exhibit maximal extraction ability in dichloroethane solutions. For reagents of the second group, a correlation between the values of the effective extraction constants of zinc and lead with the values of the Hammet s constants of substituents in the phenyl radical is observed. Chloroform appears to be the best diluent. Unlike diantipyrylmethane derivatives which extract lead better, phenyl-di-(1-hexyl-5-hydroxy-3-methyl-4-pyrazolyl)methane derivatives show better extraction ability to zinc ions. Replacement of the aliphatic hexyl substituent in the first position of the pyrazole ring with more electronegative substituents, phenyl or 2-pyridyl-, leads to the worsening of extraction ability. Extraction of zinc and lead ions by phenyl-di-(5-hydroxy-3-methyl-1-phenyl-4-pyrazolyl)methane and phenyl-di-(5-hydroxy-3-methyl-1-(2-pyridyl)-4-pyrazolyl)methane is practically absent.