The phase-transfer agents tri-n-octylethylammonium bromide and mesylate (TEABr and TEAMs, respectively) strongly catalyze the reaction of p-nitrophenyl diphenyl phosphate (p-NPDPP) with benzimidazolide ion ( ) and naphth-2,3-imidazolide ion (NI-). In dilute TEABr and TEAMs reactions are of greater than first order with respect to substrate, areneimidazole, and TEABr or TEAMs, suggesting that reaction is occurring in small aggregates of the three solutions. The reaction of p-NPDPP with OH- is not catalyzed by TEABr. The solubility of TEAMs allows study of the catalysis up to 2 X 10-2 M, and the first-order rate constants, k∞, for reaction of the areneimidazoles with p-NPDPP go through maxima with increasing [TEAMs]. The constants depend upon [p-NPDPP] at low [TEAMs] but not at high. The rate maxima can be explained in terms of incorporation of both p-NPDPP and in aggregates of TEAMs, and the rate constants of reaction in the aggregates can be estimated and are similar to that for reaction in micelles of cetyltrimethylammonium bromide (CTABr). The reactions of areneimidazolide ions with p-NPDPP are catalyzed by CTABr at concentrations below the critical micelle concentration (cmc) in water. Under these conditions the order with respect to p-NPDPP is less than 1 and catalysis appears to be due to induced micelle formation.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry