Silver (1) is involved in an efficient catalysis of the oxidative decarboxylation of acids by peroxydisulfate ion in aqueous solutions. The rate of decarboxylation is first order in silver(1) and peroxydisulfate, but zero order in carboxylic acid. The formation of alkane, alkene, alcohol, and ketone as products are attributed to alkyl radical intermediates. The synergistic effect of copper(I1) as a cocatalyst occurs at low concentrations, and is associated with the efficient trapping of alkyl radicals. The product distribution and the stoichiometry of the oxidative decarboxylation can be deliberately altered by considering the mechanistic effects of silver(I), copper(II), and carboxylic acid concentrations. A mechanism is proposed in which the silver(I1) species is formed as a metastable intermediate and it plays an important role in the specific and efficient oxidation of the carboxylic acid function.he readily available peroxydisulfate ion, SZO~*-, is

Silver (II) pieolinate, bis ( , a '-bipyridine )silver (II) nitrate, and silver oxide have been employed directly in the oxidative decarboxylation of acids. Excellent yields of carbon dioxide, isobutylene, and -butyl derivatives are obtained from pivalic acid by oxidation with all three silver(II) oxidants under a variety of conditions. The (butyl cation is the precursor for the butyl products. The decarboxylation is postulated to occur via two successive 1-equiv processes, in which the oxidation of the carboxylate moiety by silver(II) yields carbon dioxide and an alkyl radical followed by further oxidation of the alkyl radical to the cation by a second silver(II) species.

A Versatile Mechanistic Probe for Three EnzymesIn an earlier publication (la) we described an experiment involving the enzymatically catalyzed hydrolysis of p-nitrophenyl acetate (PNPA) by bovine carbonic anhydrase II (BCA).Since that time, many student projects have been derived from these experiments at Seattle University and the University of Washington. They have allowed this part of our biochemistry laboratory activities to be expanded to include enzyme assays for two additional enzymes that also exhibit esterase activity. The reaction of eq 1 is versatile: It is catalyzed not only by carbonic anhydrase but also by a-chymotrypsin (a-CT) and acetylcholinesterase (AcCE). Thus, a single reaction, conveniently monitored, serves as a pedagogic tool and a mechanistic probe for

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The solvent isotope effect (kD20/kH20 = 2.43), the dependence of rate on acidity (log k+ = -Ho + constant), and the effect on the rate of changing per cent dioxane in dioxane-water mixtures have been determined for the acid-catalyzed hydrolysis of sodium phenyl sulfate. The results are compared with the corresponding data for the hydrolysis of sodium methyl selenate, a reaction which is known to proceed cia an A-2 type mechanism. The comparison strongly indicates that the hydrolysis of the aryl sulfate ion involves the A-I type mechanism shown in eq 4. An explanation of how the observed effect of Ar group structure on rate of hydrolysis of ArOS03-can be accommodated to this mechanism is presented.