Comparative reactivities have been determined for the cleavages of p-n
itrophenyl phosphotriester substrates 4-9, and 12, and 13 by iodosoben
zoate (1) and iodosonaphthoate (11) in micellar cetyltrimethylammonium
chloride at pH 8. The aggregate substrate reactivities can be manipul
ated by altering the phosphate substituents, with each PhO-to-MeO or -
EtO change worth similar to 1 order of magnitude decrease in the rate
constant. With 2 PhO/EtO mutations, the reactivity of 4 is 470 times g
reater toward 1 than that of 5, and the differential increases to 1080
with nucleophile 11. Phosphodiester substrates such as 10 are inert t
o micellar 1. Reactivity differences can be amplified by covalent atta
chment of the substrate moiety to cationic surfactants (12 and 13), wh
ere the PhO/EtO changes induce 600-700-fold reactivity diminutions wit
h nucleophiles 1 and 11. The differential reactivities of the various
substrates reflect both innate reactivity differences and differences
in binding to the micellar pseudophase.