Catalytic hydrolysis of phosphodiesters by nucleophilic ions in gemini micellar media

Abstract

The catalytic hydrolysis of bis(4-nitrophenyl)phosphate (BNPP) and bis(2,4-dinitrophenyl)phosphate (BDNPP) catalyzed by α-nucleophiles in gemini micellar media was investigated at 27 °C. The cationic gemini surfactants, i.e., alkanediyl-α-ω-bis(hydroxyethylmethylhexadecylammonium bromide) (16-s-16 MEA 2Br−, where s = 4 and 6) were used. Nucleophilic reactivity of α-nucleophiles such as hydroperoxide (HOO−), acetohydroxamate (AHA−), and butane 2,3-dione monoximate ions (BDMO−) were compared. The kinetic rate data were treated by applying the pseudophase model. The cationic gemini surfactants show unusual rate acceleration toward the cleavage of phosphodiesters with nucleophiles. These studies reveal that the hydroperoxide ion shows the highest catalytic activity reported so far with an unprecedented acceleration rate, 107 times faster than that of the uncatalyzed reaction. The possible mechanism for the BNPP and BDNPP cleavage promoted by α-nucleophiles is proposed on the basis of kinetic analysis. Copyright © 2014 John Wiley & Sons, Ltd.