Methylbenzyl radical

Arnold s scale is derived for the action of a single substituent on the benzylic 7c-system. It cannot be used to estimate the influence of several substituents on the system under consideration. In this way it is, therefore, not possible to gain insight into the problem of captodative stabilization of a radical centre. The investigation of the spin-density distribution in benzylic radicals has been extended (Korth et al., 1987) to include multiple substitution patterns. Three types of benzylic radicals were considered a,p-disubsti-tuted a-methylbenzyl radicals [17], a-substituted p-methylbenzyl radicals [18] and a-substituted benzyl radicals [19]. In [17] and [18] the hyperfine coupling constants of the methyl hydrogens were used to determine the spin-density... 

Values of kd/kc of 0.055 and 0.28 (kd is the rate constant for the disproportionation process and kc is that for the coupling process) were measured for cumyl radicals (36) in benzene and on silica, respectively (Scheme 21) [161], Similarly, increases in the yields of disproportionation products have been observed for a-methylbenzyl radical pairs at low temperature on porous glass and several types of silica [101]. For example, kd/kc ratios of 0.054 and 1.33 were obtained in pentane and on porous glass at... 

Methylphenylethanoic acid radical cation undergoes decarboxylation leading to the 4-methylbenzyl radical with /c = 1.5 x 10 s at pH = 0.3 (Scheme 69, X = Me). 

Entry 1 is a chlorination at a stereogenic tertiary center and proceeds with complete racemization. In Entry 2, a tertiary radical is generated by loss of C=0, again with complete racemization. In Entry 3, an a-methylbenzyl radical is generated by a fragmentation and the product is again racemic. Entry 4 involves a benzylic bromination by NBS. The chirality of the reactant results from enantiospecific isotopic labeling of ethylbenzene. The product, which is formed via an a-methylbenzyl radical intermediate, is racemic. 

Another possibility is that, as in polycondensation, the formation of per-chloro-p-methylbenzyl radical is also brought about by iodide ion, but its subsequent reaction with iodide ion occurs so fast that its dimerization to perchloro-p,/7 -dimethylbibenzyl or subsequent vicinal chlorine elimination is prevented. Accordingly, when the reaction is carried out in the presence of toluene as hydrogen-atom donor (see preceding section) the yield of per-chloro-p-xylylene diminishes (72%), the rest being a, a //-octachloro-p-xylene, benzyl acetate, and, according to H-nmr spectroscopy, a mixture of cis- and tra 5-a/7,a //-tetradecachlorostilbene (46) (Diaz-Alzamora, 1968). 

The benzyl radical is the reaction product of the abstraction path (path a) of the reaction of toluene with OH. Similarly, methylbenzyl radicals are formed during the OH abstraction reactions with xylenes and trimethylbenzenes. We have measured the reaction rate constants with O2, NO and NO2 of a series of benzyl-type radicals, including a few fluorosubstituted ones in purpose of comparison. 

In an oxygen atmosphere, acetophenone is the only product due to the reaction of oxygen with the a-methylbenzyl radical however, in the photolysis of 2-PPA in a zeohte slurry and as a solid complex under an oxygen atmosphere, only a minor amount of acetophenone is obtained along with considerable... 

X includes ortho- (6) and para- (7) coupled products of a-methylbenzyl radical. 

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