Effect of changes in surfactant structure on micellarly catalyzed spontaneous decarboxylations and phosphate ester hydrolysis

Abstract

Micelles of the zwitterionic surfactant, N,lV-dimethyl-lV-dodecylglycine, catalyze the spontaneous decarboxylation of 6-nitrobenzisoxazole-3-carboxylate ion 170-fold and that of cyanophenyl acetate ion 690-fold, and they, and micelles of the corresponding alanine surfactant, are better catalysts than dodecyltrimethylammonium bromide by factors of almost 3-fold. The catalytic efficiency of cationic micelles of JV,lV-dimethyl-jV-hydroxylethyl-2hexadecylammonium bromide is also increased 2-fold by conversion of this surfactant into a zwitterion at high pH. Lecithin and lysolecithin are very poor catalysts, showing that the arrangement of charge in the zwitterionic head group is of key importance. Catalysis by micelles of IV.lV-dimethyl-iV-dodecylglycine is subject to large salt effects which depend upon the anion, but differ from those typical of micellar catalysis. Salts having hydrophilic anions tend to increase catalysis and those having hydrophobic anions decrease it. Chemically inert solutes such as phenols and aliphatic amines change the catalytic effectiveness of micelles of cetyltrimethylammonium bromide, but these micelles in aqueous ethylene glycol, or the reverse micelles in hexanol-water, are poor catalysts both for decarboxylation and for the spontaneous hydrolysis of 2,4-dinitrophenyl phosphate dianion.

Accelerated decarboxylation of 6-nitrobenzisoxazole-3-carboxylate in imidazolium-based ionic liquids and surfactant ionic liquids

“…This can be related to polarity decrease in the micellar microenvironment, as the hydrophobic moiety of the surfactant increases. A similar effect has already been observed using the same kinetic probe when comparing reactivity in cationic surfactants CTABr and in dodecyltrimethylammonium bromide (DTABr) [19], and also in zwitterionic sulfobetaine surfactants dimethyltetradecylammonium propane sulfonate (SB3-14) and dimetylcetylammonium propane sulfonate (SB3-16), as shown in Table 1 [20]. As regards the counterion effect, the systems with bromide are better catalyst than the systems with chloride ion (Table 1).…”

Non-cross-linked and cross-linked poly(alkylmethyldiallylammonium halides): synthesis and aggregation behavior

“…Recent analysis of solvent effects on this reaction clearly revealed the importance of hydrogen bonding and ion pairing effects as the major contributing factors in determining the decarboxylation rates. [77][78][79][80] The unimolecular decarboxylation of 6-NBIC provides a popular probe for exploring micellar, [81][82][83][84][85][86][87] polymer 19,20,[88][89][90][91][92] and antibody catalysis. [93][94][95] The rate accelerations can be largely ascribed to partial dehydration of the carboxylate function of the initial state in the hydrophobic microenvironment at the binding site of 6-NBIC.…”

“…81 The micelle-catalyzed decarboxylation reactions of 6-NBIC have been regarded as useful models for electrostatic and hydrophobic interactions in biological systems to provide information regarding the mechanism of regulation of reactions occurring on membranes. [81][82][83][84][85][86]…”

Ion-Binding Properties of Crown Ether and Cryptand Containing Polymers

“…Hence, the catalysis can be selectively controlled by adding alkali or alkaline earth cations, the rate of decarboxylation being dependent on the nature and concentration of the cation. A summary of rate constants for this decarboxylation in the presence of different micelles and polymers is given in Table III (7,25,55). The catalytic factor is highest for the Cs+ charged P18C6 polymer, the rate constant of the bound carboxylate being 14000 times the value of the unbound ion.…”