Benzene methyl affinity

Szwarc and his co-workers have measured the methyl affinities (that is, reactivities toward methyl radicals compared with that of benzene) of a number of heterocyclic compounds. These, together with the methyl affinities of some homocyclic compounds, are set out in Table IX. 

A very early indication that C-nitroso-compounds are particularly susceptible to radical attack was the methyl affinity value of 105 determined for nitrosobenzene (Heilman el al., 1957). This figure reflects the reactivity of nitrosobenzene, relative to that of benzene, towards attack by methyl radicals. It was apparently several years before this reactivity was linked with nitroxide formation... 

Goldschmidt and Beer.372 The 2-alkylated product is the main one formed. This orientation is not unexpected since, compared with the phenyl radical, an alkyl radical should have some nucleophilic character. The j8-/y- ratio is also lower than in the phenylation, as expected for a more nucleophilic radical.371 Pyridine has a methyl affinity of 3 compared with benzene.373 This, however, does not represent the relative amount of picolines and toluene formed with acetyl peroxide.371... 

Methyl cation affinities of benzene and some substituted benzenes have been calculated. These follow a simple additivity rule and the value for benzene shows good agreement with the experimental estimate. Conclusive evidence is presented that these values are linearly related to the corresponding proton affinities. The competition between deuteriation and alkylation in the reaction of radiolytically formed perdeuterio ethyl cations with iV-methylpyrrole and with thiophene has been studied. Deuteriation, the Brpnsted acid pathway, predominates and intramolecular selectivities have been determined for each reaction. ... 

Benzopurpurine 4B, formula (15), is coplanar and highly substantive, but the isomeric compound, formula (16), has two methyl groups in such positions that they prevent the two benzene nuclei from lying in the same plane, and the affinity of cellulose for the substance is therefore low. 

The first reaction was found by Levy and Szwarc to be predominant when methyl radicals attacked isooctane. The second reaction is predominant, however, for aromatic hydrocarbons. The free radicals formed in the above two reactions will react with each other, with other free radicals, or with impurities. The affinity of the methyl radical to attack an aromatic increases in the following order benzene, diphenyl ether, pyridine, diphenyl, benzophenone, naphthalene, quinoline, phenanthrene, pyrene, and anthracene. The ability of free alkyl radicals to interact with isopropylbenzene and cyclohexene decreases in the following order methyl, ethyl, propyl, butyl, isopropyl, sec-butyl, and tertiary butyl. 

Anisole (methylphenylether) can be regarded as methylated phenol and has been proposed (Kauppda 2004a) as a suitable dopant for APPI of analytes with low proton affinity (PA) values in reverse phase HPLC solvents in which benzene and toluene are unsuitable. Previously only acetone was used in these conditions but its fairly high PA (812kJ.mop ) meant that it was suitable for only analytes with even higher PA values. It was shown... 

BzA was polymerized in a higher yield than BA, in spite of the greater bulkiness of the benzyl group. This seems to be the result of a high affinity of the aromatic group to poly(NMAAm), which causes BzA monomer to proceed easily to an active center. Poly(NMAAm) swells considerably in aromatic solvents such as benzene, acetophenone and methyl benzoate, but not in the aliphatics such as acetone, acetonitrile and AcOEt. However, the block copolymer yield in the BzA system was lower than with other acrylates. This is attributed to the participation of labile benzylic hydrogen of BzA in chain transfer reactions. 

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