Zn(II)-Catalyzed Cleavage of 2-Hydroxypropyl p-Nitrophenyl Phosphate in Gemini 16-6-16 Micelles

Abstract

Hydrolytic cleavage of 2-hydroxypropyl p-nitrophenyl phosphate (HPNP) catalyzed by Zn(II)-biap (biap: N, N- bis (2-ethyl-5-methyl-imidazole-4-ylmethyl) aminopropane) complex was investigated spectrophotometrically in a cationic Gemini surfactant 16-6-16 [Bis(hexadecyldimethylammonium)hexane bromide] micellar solution. Effects of various factors (pH, [complex], temperature [K], amine additives, etc.) on the catalytic cleavage of HPNP were evaluated systematically. Experimental observations showed that higher rate acceleration of HPNP cleavage promoted by Zn(II)-biap complex was obtained in the 16-6-16 micellar solution in comparison with the background value (k _o) of HPNP cleavage. Compared with the ZnL + G(16-6-16) system, the results reveal that a 1.2 ∼ 2.9 folds rate enhancement was given in the catalytic systems containing diethylenetriamine (DETA). Additionally, the addition of diethylenetriamine (DETA) resulted in a 1.2 ∼ 2.7 folds higher rate enhancement in contrast with 1,2-Ethylenediamine (EDA).

Keywords:

• Amine additives
• Gemini 16-6-16 micelles
• HPNP cleavage
• Zn(II)-biap complex

Acknowledgments

This work was supported by Scientific Research Foundation for the PhD (Sichuan University of Science & Engineering, No. 07ZR14) and Key Project of Sichuan Province Education Office (No. 08ZA160).

Notes

^a I = 0.1 mol·L⁻¹KNO₃, [HPNP] = 2.0 × 10⁻⁵mol·L⁻¹, [16-6-16] = 1.0 × 10⁻⁴ mol·L⁻¹, pH7.00 ∼ 9.00.