Toluene methyl radical

Thermal decomposition of 1-methyl-A -phospholen in toluene at 356-444 °C yielded butadiene as the primary product. The activation parameters are in agreement with a mechanism involving ring opening to a biradical followed by fragmentation into butadiene, phosphorus, and methyl radicals. ... 

Fig. 4. Arrhenius plots for the pressure-dependent flow system decomposition of dimethyl mercury. 1, Gowenlock, Polanyi and Warhurst (7 torr C02+3 torr toluene), Kominar and Price (4.4 torr toluene) 2, Price and Trotman-Dickenson (16 torr toluene, rate coefficients corrected for methyl radicals found as ethylbenzene) 3, Krech and Price (16 torr benzene). O, Lossing and Tickner (6-20 torr helium).

Fig. 5. The Arrhenius plot of kl/k2i. e, dimethyl zinc O, trimethyl gallium , trimethyl indium. % figures are in terms of the theoretical yield of methyl radicals that would be obtained if all methyl-metal bonds were broken. All points are corrected to 13 torr pressure (toluene+0.3-2.5 % alkyl).

The H2—02 radical pool that then develops begins the reactions that cause the fuel concentration to decay. The most effective attackers of the methyl side chain of toluene are OH and H. OH does not add to the ring, but rather abstracts a H from the methyl side chain. This side-chain H is called a benzylic H. The attacking H has been found not only to abstract the benzylic H, but also to displace the methyl group to form benzene and a methyl radical [69], The reactions are then... 

The polar effect was at first invoked to explain various directive effects observed in aliphatic systems. Methyl radicals attack propionic acid preferentially at the a-position, ka/kp = 7.8 (per hydrogen), whereas chlorine " prefers to attack at the /3-position, ka/kp = 0.03 (per hydrogen). In an investigation of f-butyl derivatives, a semiquanti-tative relationship was observed between the relative reactivity and the polar effect of the substituents, as evidenced by the pK, of the corresponding acid. In the case of meta- and / ara-substituted toluenes, it has been observed that a very small directive effect exists for some atoms or radicals. When treated by the Hammett relation it is observed that p = —0.1 for H , CeHs , P-CH3C6H4 and CHs . On the contrary, numerous radicals with an appreciable electron affinity show a pronounced polar effect in the reaction with the toluenes. Compilation of Hammett reaction constants and the type of substituent... 

Table 3 Calculated A//rxn Values for Halide Radicals Abstracting Hydrogens from Aromatic Ring of Benzene or Toluene Methyl Group...

They used toluene as carrier gas, and in addition found small amounts of methane and dibenzyl, presumably formed from toluene by the obvious reactions. Rebbert and Laidler state that they were using the toluene carrier gas technique of Szwarc, but in fact they were attempting to use it under conditions where it has no apparent advantage. Szwarc intended that the toluene should mop up the radicals formed by the initial bond fission of the compound under investigation, but clearly this did not happen at the temperatures used here (200-240° G). In fact, the recombination of methyl radicals, which requires no activation energy, is more likely to... 

Oxidation.—Oxidizing agents which attack benzene with difficulty react readily with toluene, and the substituted methyl radical becomes oxidized to carboxyl. 

This oxidation of the methyl radical to carboxyl emphasizes a difference between benzene compounds and aliphatic compounds for in the latter, it will be recalled, the direct oxidation of a methyl group to a carboxyl group is impossible. Only one toluene is known which agrees with the theory as only one mono-methyl benzene is possible. 

High intensity irradiation of dibenzyl ketone in hexane/isopropanol mixtures yields 1,2-diphenyl ethane and toluene as the sole products. A study of the photochemical behaviour of dibenzyl ketone adsorbed on zeolites has been carried out and the results found to be dependent upon the Sl/Al composition of the zeolite. A laser flash examination of the behaviour of dibenzyl ketone in Nafion membranes has demonstrated that a modest yield of benzyl cations is formed. A study of the physical photochemistry of the ketone (1) has shown that the excited state is a carbonyl localized singlet state. This ultimately decays to afford a naphthalene localized triplet state. Norrish Type I cleavage does occur from the singlet state to afford products derived from the radicals (2) and (3). The authors report also that the 1-naphthyl methyl radical is formed from the triplet state. A study of the modification of the photochemical behaviour of the a-alkyldibenzyl ketones (4) by complexation in... 

How are we to account for the stability of the benzyl radical Bond dissociation energies indicate that 19 kcal/mole less energy (104 — 85) is needed to form the benzyl radical from toluene than to form the methyl radical from methane. 

If the particular reaction studied is the unimolecular decomposition of a free radical, such as (3), then the use of a trap will enable the effective concentration of the radical to be measured. A radical trap will indicate the presence or absence of a free radical reaction and may sometimes provide evidence for a partly or entirely molecular reaction. Rate data for free radical reactions are derived assuming the occurrence of a steady state concentration of radicals. The time required to produce a steady state concentration of methyl radicals in the pyrolysis of AcH is shown for various temperatures in Fig. 1. Realistic values for rate coeflBcients may be obtained only if the time of product formation is long compared to the time to achieve the steady state concentrations of the radicals concerned. Thus deductions from the results from the bromination of isobutane , neopentane , and toluene have been criticised on the grounds that a steady state concentra-... 

Additional experiments were conducted in which toluene and iodine vapors were passed through the RF. discharge together. Table III shows the composition of the condensable products formed in this experiment. In view of the known affinity of iodine for free radicals (3), the formation of benzyl iodide, iodobenzene, and methyl iodide together with greatly reduced amounts of the previously observed products argues for the presence of benzyl, phenyl, and methyl radicals in the discharge. 

Oxidation of toluene by lead tetraacetate in the absence of O2 gives benzyl acetate, methyl benzyl acetates, toluic acids, and xylenes. Lead acetate pyrolyzes to give methyl radicals and carbon dioxide ... 

Methyl radicals either add to toluene to give xylenes, or abstract a H-atom from acetic acid or toluene. The products other than the xylenes are produced by the reactions shown in equation (j)... 

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