THE ROLE OF METAL (HYDR) OXIDES IN CATALYZING THE HYDROLYSIS OF QUINALPHOS

Abstract

Catalysis of the hydrolysis of the organ phosphorus compound, quinalphos (Q) by (hydr) oxides was studied at pH 4.0, 7.0, and 10.0, and at 25^oC. FeOOH and Al(OH)₃ were the used solids for this research. Catalysis of quinalphos was followed by determining the disappearance of Q and the appearance of 2-hydroxyquinoxaline (HQ) product in the absence and presence of (hydr) oxides using HPLC with UV detector. Under these conditions, both hydroxides (FeOOH and Al(OH)₃) have catalyzed the hydrolysis of quinalphos. In this study, FeOOH was found to be the best catalyst at the used pHs. It is apparent that at pH 10.0, K_obs for disappearance of Q is almost equal to that for the appearance of HQ, which indicates that hydrolysis of Q at pH 10.0 follows S_N2 (P) pathway. On the other hand, at pH 4.0 and 7.0, hydrolysis of Q may have followed two pathways, S_N2 (P) and S_N2 (C), as K_obs for producing HQ is smaller than that for loss of Q.