Methylene Chloride, proton transfer

Although the o-xylylene complex is thermally unstable, it was characterized at — 50 °C by its 1H- and 13C-NMR spectra showing the exocyclic methylene at 5 = 5.04,4.42 ppm (JH) and 5 = 144.8 ppm (13C) using C6D5CD3 as the solvent. Its reaction with benzoyl chloride on the exocyclic carbon leaves a very acidic methylene group which transfers a proton onto the adjacent methylene unit. The double bond is benzoylated again in in situ and a di-cation of the [bis(arene)Fe]2+ type is obtained [47] Scheme VIII. 

In certain cases the process analogous to the isonitrile synthesis for the preparation of phosphaalkenes, showing proton- and halogene-substituted C-bridged atoms, is a successful one. 2,4,6-tri-i-butylphenyl-phosphane can be transferred to the phosphaalkene using a strong alkaline solution of chloroform [Eq. (7)] or methylene chloride [Eq. (8)]. A carbene addition mechanism is involved in this reaction (36, 37). 

Sangalov et al., prepared arenonium ions in the form of Gustavson complexes starting from various substituted benzenes, hydrogen chloride and aluminium chloride. These complexes were drown to be active initiators for the polymerisation of styrene and isobutene at —30 and —78°C in methylene chloride. No kinetic investigation was carried out on these systems. The authors claimed that initiation took place by protonation of the olefin and that incorporation of aromatic groups from the cataylst in the products was due to transfer reactions. 

Electrochemical methods have played an important role in the recognition of cation radicals as intermediates in organic chemistry and in the study of their properties. An electrode is fundamentally an electron-transfer agent so that, given the proper solvent system, anodic oxidation allows formation of the cation radical without any associated proton or other atom transfer and without the formation of a reduced form in the immediate vicinity of the cation radical. Moreover, because the potential of the electrode can be adjusted precisely, its oxidizing power can be controlled, and further oxidation of the cation radical can often be avoided. Finally, the electrochemical experiment can involve both production of the cation radical and an analysis of its behavior, so that information about the thermodynamics of its formation and the kinetics of its reaction can be obtained, even if the cation radical lifetime is as short as a few milliseconds. There are some limitations, however, in the anodic production of cation radicals. The choice of solvent is limited to those that show reasonable conductivity with a supporting electrolyte (e.g. tetra-n-butylammonium perchlorate, TBAP). Acetonitrile, methylene chloride and nitrobenzene have been employed as solvents, but other favorites, such as benzene and cyclohexane, cannot be used. The relatively high dielectric constant of the suitable... 

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