TEMPERATURE EFFECTS UPON THE MICELLAR-ASSISTED CYCLIZATION OF O-3-HALOPROPYLOXYPHENOXIDE ION

Cationic micelles of dodecyl and cetyltrimethylammonium bromide (DoTABr and CTABr) and of cetyltributylammonium bromide (CTBABr) speed cyclizations of o -3-halopropyloxyphenoxide ion (halo = bromo, iodo; 1a and 1b, respectively) by decreasing enthalpies of activation. Decreases are larger with 1b and 1a and in the sequence DoTABr < CTABr < CTBABr. Measurements of 1 H NMR chemical shifts of a model, a 2-methoxyphenoxide ion, and the surfactants at 25 and 60°C show that the micellar rate enhancements depend on a balance between interactions of the ammonium ions with the phenoxide residue of 1a and 1b and the excess halide ion. Temperature-induced changes in micellar structure appear to have little effect upon the values of the activation parameters. © 1993 Academic Press, Inc.