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Benzyl formate, radiolysis

Triorganyl-sulfonium, -selenonium and -telluronium salts are reduced by carbon dioxide radical anions/solvated electrons produced in aqueous solution by radiolysis. The radical expulsion accompanying reduction occurred with the expected leaving group propensities, i.e. benzyl > secondary alkyl > primary alkyl > methyl > phenyl. Much higher product yields in the reduction of selenonium and telluronium compounds have been accounted for in terms of a chain reaction with carbon-centred radicals, with formate serving as the chain transfer agent.282... [Pg.118]

Radiation-Induced Polymerization. Polymerization induced by irradiation is initiated by free radicals and by ionic species. On very pure vinyl monomers, D. J. Metz demonstrated that ionic polymerization can become the dominating process. In Chapter 12 he postulates a kinetic scheme starting with the formation of ions, followed by a propagation step via carbonium ions and chain transfer to the vinyl monomer. C. Schneider studied the polymerization of styrene and a-methylstyrene by pulse radiolysis in aqueous medium and found results similar to those obtained in conventional free-radical polymerization. She attributes this to a growing polymeric benzyl type radical which is formed partially through electron capture by the styrene molecule, followed by rapid protonation in the side chain and partially by the addition of H and OH to the double vinyl bond. A. S. Chawla and L. E. St. Pierre report on the solid state polymerization of hexamethylcyclotrisiloxane by high energy radiation of the monomer crystals. [Pg.9]

The absorption due to the substituted benzyl type polymer radical, Pi is observed in pulse radiolysis of CMS solutions in cyclohexane and THF. An electron in cyclohexane or THF reacts with CMS resulting in formation of Pi and Cl by dissociative electron capture (reaction (10)). [Pg.41]

Fig. 2 (a) shows the absorption spectra observed in CMS films following pulse radiolysis. There is no evidence of formation of excimer, triplet, or phenyl anion as observed in pulse radiolysis of polystyrene film (14) suggesting that these transient species or their precursors are scavenged by the chloromethyl group. Instead, absorption spectra with double peaks around 320 nm due to a substituted benzyl type polymer radical and the complex of phenyl rings and chlorine atoms are observed. [Pg.41]

The one-electron reduction potentials of the radical cations of thioanisole, benzyl methyl sulphide, and 2-hydroxyethyl benzyl sulfide in water and several organic solvents were investigated by cyclic voltammetry. For comparison, the one-electron oxidations in water were also measured using pulse radiolysis. ° The two methods are complementary and the reversible potentials determined by pulse radiolysis are fairly close to the peak potentials determined by cyclic voltammetry (Table 8) indicating that the peak potentials do correspond to the formation of sulfur radical cations for all three sulfides. [Pg.454]

Neta and Behar measured the rate constants for intramolecular electron transfer for an extended series of aryl (ArX) and benzyl halide (ArCH2X) radical anions bearing an electron withdrawing ring substituent (NO2, CN, COCH3), generated by pulse radiolysis in aqueous solution (Table 12), conditions under which spectroscopic evidence for formation of the intermediate radical anions was obtained [281-284]. [Pg.1225]

By contrast with PMMA, poly(methyl acrylate), PMA, and several other aliphatic polyacrylates were found by Shultz and Bovey (240) to imdergo cross-linking and gel formation on irradiation with 1-MeV electron beams. They reported G(S) = 0.15 and G(X) = 0.52 for PMA. Graham (241,242) reported that the phenyl, benzyl, and 2-phenyl ethyl acrylate polymers also undergo cross-linking on y radiolysis imder vacuum. There was evidence of side-chain scission also, and according to Fox and co-workers (243,244) the major volatile products were similar to those observed for PMMA. [Pg.6860]


See other pages where Benzyl formate, radiolysis is mentioned: [Pg.374]    [Pg.71]    [Pg.90]    [Pg.99]    [Pg.364]    [Pg.315]    [Pg.78]    [Pg.140]   
See also in sourсe #XX -- [ Pg.90 , Pg.99 ]




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Benzyl radiolysis

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