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.
ethyl diphenylcarbamate, and diphenylamine are from Distillation Products Industries. p-Nitrophenyl diphenylcarbamate is from Sigma Chemical Co. Dimethylcarbamoylpyridinium chloride was prepared by the method of Johnson and Rumon.21 Diphenylcarbamoylpyridinium chloride, mp 107.5-108.5°, was prepared by the method of Herzog.22 Diphenylcarbamoyl fluoride, mp 81.8-82.0°, was prepared by allowing equimolar KF and diphenylcarbamoylpyridinium chloride to react in 10% acetonitrile, and twice recrystallized from ethanol. This product has the same melting point as the diphenylcarbamoyl fluoride obtained by treatment of diphenylcarbamoyl chloride with SbF3 in xylene.5 The mercaptoethanol thiol ester of diphenylcarbamic acid was prepared from the treatment of II, 0.10 , with 0.2 M mercaptoethanol, pH 8.0, for 5 min. The product was isolated in 89% yield in the crude form and recrystallized from ethanol, mp 77.5-78.5°. Elemental analysis was performed by Schwarzkopf
A spectrophotometric stopped-flow kinetic study of the permanganate ion oxidation of furfural (I) and six 5-substituted furfurals at pH 11.5-13.3 reveals that the reaction follows two reaction paths. The minor pathway (Scheme I) is independent of hydroxyl ion concentration, and the major mechanism (Scheme II) is dependent on the first power of hydroxide ion concentration. Both reaction pathways are first order with respect to the concentration of I and permanganate ion. A correlation of the second-order rate constants with Hammett roeia-substituent constants has been observed for the substituents 5-Me, 5-Et, 5-n-Bu, H, 5-C1, and 5-Br at 25°with p = +1.30 (Scheme II). At pH 13.3 (Scheme II), AH * is 10.2 kcal/mol, AS* is -22.8 eu, and &h/&d is >1.8. Oxygen-18 experiments show that the solvent is the major source of oxygen introduced into I via Scheme II. The kinetic data are consistent with the formation of the hydrate anion of I followed by a hydride anion transfer to permanganate ion in the rate-determining step for the mechanism of Scheme II. It is postulated that the mechanism of Scheme I involves a direct attack of permanganate ion on I to give the permanganate ester, which decomposes in a subsequent slow step.
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