Benzyl chloride, flash photolysis

There have been a number of studies of magnetic fields upon radical recombination using steady-state techniques of photolysis or pyrolysis. They have variously found large or small effects, which are not always consistent with the theoretical predictions [304—306]. However, using laser flash photolysis techniques to provide fast time resolution, Turro et al. [307] followed the combination of benzyl radicals within hexadecyltrimethyl ammonium chloride micelles in water. The combination occurs over times < 100 ns. A magnetic field of 0.04 T reduces the rate of recombination by almost a factor of two. Such a magnetic field... 

To our knowledge, 46 has never been observed in solution under stable conditions, even at low temperature. Pulse radiolysis " of benzyl chloride as well as flash photolysis ° of several derivatives in HHP have allowed the observation of the electronic absorption spectra of benzyl and its 4-methyl and 4-methoxy derivatives. The and NMR spectra of the 2,4,6-trimethylbenzyl cation and other more heavily substituted benzyl cations, however, have been studied at low temperature in superacid media. In the gas phase, cold benzyl radical has been probed by two-color, resonant two-photon ionization techniques, thus providing very accurate vibrational frequencies below 650 cm for the benzyl cation. Furthermore, the adiabatic ionization energy of benzyl radical and several isotopomers in the ground state were determined from their threshold photoionization spectra using resonant two-photon excitation and detection of electrons by pulsed field ionization. This information, combined with Af//° (CgH5CH2) from Ref. 212 leads to the value of Af//°m(46) reported in Table 9. 

The reaction of a series of substituted styrene radical cations with anions has recently been studied in detail by laser flash photolysis. Representative kinetic data are summarized in Tables 3 and 4 and demonstrate that most of the anions studied react with styrene radical cations with diffusion controlled rate constants. These reactions can involve either addition to the p-carbon to give a benzyl radical (Eq, 15) as discussed above or electron transfer to regenerate the precursor alkene plus the oxidized nucleophile (NU , Eq. 16). Transient absorption spectra have been used to distinguish between these two possibilities. For example, reaction of the radical cation with either bromide or chloride leads to the formation of a transient that is identified... 

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