Radicals with olefins, relative rate constants

With cyclohexyl radicals the opposite behavior is seen. Relative rate constants arc reduced and the preference for tail addition is reinforced. For olefins substituted with electron-donor substituents, nucleophilic radicals give the greatest tail v.v head specificity. The converse generally also applies. 

Relative Rate Constants for Reaction of Radicals With Olefins(13)... 

Rate constants for the reaction of hydroxyl radicals with different compounds were determined by Haag and Yao (1992) and Chramosta et al. (1993). In the study of Haag and Yao (1992) all hydroxyl radical rate constants were determined using competition kinetics. The measured rate constants demonstrate that OH0 is a relatively nonselective radical towards C-H bonds, but is least reactive with aliphatic polyhalogenated compounds. Olefins and aromatics react with nearly diffusion-controlled rates. Table 4-3 gives some examples comparing direct (kD) and indirect (kR) reaction rate constants of important micropollutants in drinking water. 

The reductive hydrodimerization of activated olefins was considered as a good test system for initial SECM studies, due to the fact that the dimerization rate constant could be tuned via the substituent activating the olefinic double bond." " For the relatively slow dimerization of the dimethyl fumarate (DF) radical anion, a large UME (25 jam diameter Pt electrode) was employed so that the value of K2 (Equation 7.19) was in the range where the SECM response would be sensitive to the kinetics. Experiments were carried out with solutions of 5.15 and 11.5mM DF in dimethylformamide (DMF), containing 0.1 M tetrabutylammoniumtetrafluoroborate as a supporting electrolyte. The oxidation of -tetramethyl-l,4-phenylenediamine (TMPD), included in solutions at a con-... 

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