Organic reaction mechanisms isotope effects

Use of Isotopic Effects in the Determination of Electro-Organic Reaction Mechanisms. Much work has been carried out on the mechanism by which hydrocarbons can be clectrochemically oxidized. Were that easy, it might be possible to use available oil in electrochemical devices (fuel cells) to convert chemical to electrical energy 2—3 times more efficiently than do heat engines (Chapter 13). 

By use of especially selected aromatic substrates—highly hindered ones—isotope effects can be detected in other kinds of electrophilic aromatic substitution, even in nitration. In certain reactions the size of the isotope can be deliberately varied by changes in experimental conditions- and in a way that shows dependence on the relative rates of (2) and the reverse of (I). There can be little doubt that all these reactions follow the same two-step mechanism, but with differences in the shape of potential energy curves. In isotope effects the chemist has an exceedingly delicate probe for the examination of organic reaction mechanisms. 

Secondary a-deuterium kinetic isotope effect proved to be very useful in distinguishing between the organic reaction mechanisms of dissociative (S]sj 1) and associative (Sj 2) types. A. Streitwieser, Jr. et al. and K. C. Westa-... 

Macrocycles and other concave structures, acid-base behaviour in, 30,63 Macromolecular systems in biochemical interest, 13C NMR spectroscopy in, 13,279 Magnetic field and magnetic isotope effects on the products of organic reactions, 20,1 Mass spectrometry, mechanisms and structure in a comparison with other chemical processes, 8, 152... 

Substitution reactions, aromatic, hydrogen isotope effects in, 2, 163 Substitution reactions, bimolecular, in protic and dipolar aprotic solvents, 5,173 Sulphur, organic oxyacids of, and their anhydrides, mechanisms and reactivity in reactions of, 17, 65... 

Mechanisms, of proton transfer between oxygen and nitrogen acids and bases in aqueous solutions, 22, 113 Mechanisms, organic reaction, isotopes and, 2, 1 Mechanisms of reaction, in solution, entropies of activation and, 1, 1 Mechanisms of reaction, of /3-lactam antibiotics, 23, 165 Mechanisms of solvolytic reactions, medium effects on the rates and, 14, 10 Mechanistic analysis, perspectives in modern voltammeter basic concepts and, 32, 1 Mechanistic applications of the reactivity-selectivity principle, 14, 69 Mechanistic studies, heat capacities of activation and their use, 5, 121 Mechanistic studies on enzyme-catalyzed phosphoryl transfer, 40, 49 Medium effects on the rates and mechanisms of solvolytic reactions, 14, 1 Meisenheimer complexes, 7, 211... 

A second-order dependence on both the reductant and acidity was observed in the oxidation of alcohols with butyltriphenylphosphonium dichromate study of MeCD2OH and Me2CDOH indicated the presence of a substantial kinetic isotope effect. The reaction was studied in 19 organic solvents and the rates were correlated with mul-tiparametric equations. The reaction is susceptible to both electronic and steric effects of the substituents. A mechanism involving the formation of a dichromate ester and an a-C-H cleavage has been proposed.4... 

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