1-Methylnaphthalene, electron transfer from

Tanaka et al. (1996,2000) studied the behavior of a series of naphthalene derivatives in AN solution containing NaN02 and CF3SO3H at 0°C in air. Naphthalene showed very low reactivity, and most of the starting material was recovered after the reaction. In case of 1-methylnaphthalene, a coupling reaction took place to produce 4,4 -dimethyl-l,T-binaphthyl in 91% yield alongside mononitro derivatives of the dimer in 1.5% yield. However, when the reaction is carried out on the same conditions but in inert (Nj) atmosphere, the yield of the dimer decreased from 97 to 15%, and no mononitro derivatives were formed. Therefore, the oxidation of NO with O2 to form NO2 (after the electron transfer to NO from 1-methylnaphthalene) is an obvious step of the reaction depicted in Scheme 4.42. 

FIGURE 10.29 Typical photoproducts observed (A) in the irradiation (A = 300 nm) in air of naphthalene and 1-methylnaphthalene adsorbed on silica and formed by a Type I electron transfer (superoxide) mechanism (Barbas et al., 1993) and (B) in the irradiation in air of acenaphthylene (A = 350 nm) adsorbed on silica formed by a Type II singlet oxygen mechanism (Barbas et al., 1994) (adapted from Dabestani, 1997). 

Eberson and Radner (19-23) have explored some of the scope of the reaction of N02 with ArH +. They prepared the solid hexafluorophosphates of the naphthalene cation radical and some methylnaphthalene cation radicals, for example, C10H8,+PF6, and carried out reactions of the solid salts with N02 in dichloromethane at temperatures near-25 °C (19-23). Reaction was found to occur according to equation 12. The results of their reactions are summarized in Table I (19). This table also lists the results of nitrating the parent hydrocarbons by the conventional route (N02 + ) and with N204. The results prompted Eberson and Radner to dismiss the possibility that conventional nitration of these compounds was preceded by electron transfer (equations 11 and 12), because the proportions of isomers from the reaction of ArH + with N02 were quite different from those from the reactions of ArH with N02+ and with N204. Eberson and Radner set out to determine whether or not the conventional nitration of naphthalene and methylnaph-thalenes involved the electron-transfer step. In so doing they became, to our knowledge, the first to show that a neutral radical (N02) will react with an aromatic cation radical. 

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