- Chemistry of the cyclopentoxy and cyclohexoxy radicals at subambient temperatures
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The Cl-atom initiated oxidation mechanisms of both cyclopentane and cyclohexane have been studied as a function of temperature using an environmental chamber/FTIR technique. The oxidation of cyclohexane leads to the formation of the cyclohexoxy radical, the chemistry of which is characterized by a competition between ring-opening (R5) and reaction with O2 (R6) to form cyclohexanone. The yield of cyclohexanone is shown to increase with decreasing temperature, and a rate coefficient ratio k6/k5 = (1.3 ± 0.3) × 10-27 exp(5550 ± 1100/T) cm3 molecule-1 is obtained. The energy barrier to ring-opening is estimated to be 11.5 ± 2.2 kcal/mol. The dominant fate of the cyclopentoxy radical, formed in the Cl-atom initiated oxidation of cyclopentane, is ring-opening under all conditions studied here (230-300 K, 50-500 Torr O2), with only a minor contribution from the O2 reaction at the lowest temperatures studied. The barrier to ring-opening for the cyclopentoxy radical is probably less than 10 kcal/mol.
- Orlando, John J.,Iraci, Laura T.,Tyndall, Geoffrey S.
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p. 5072 - 5079
(2007/10/03)
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- Direct Oxidation of Methyl Ethers to Carbonyl Compounds with a Combination of Nitrogen Dioxide and Water in the Presence or Absence of Ozone
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A combination of nitrogen dioxide and water has been found to provide a new agent for the transformation of various alkyl methyl ethers 1 (R = Me) to carbonyl compounds 2 under mild conditions. The oxidation can be achieved successfully in dichloromethane, but hexafluoro-2-propanol was found to be most satisfactory as the solvent. The reaction was generally clean, and simple evaporation gave the expected oxidation product 2 in moderate to good yield. In the presence of ozone, but without water, the similar oxidation was observed only after prolonged reaction time, suggesting that some initial minor reaction with a strong oxidant, possible nitrogen trioxide, afforded an acidic promoter, which then worked as a catalyst similar to that involved in the reaction with a nitrogen dioxide and water system.
- Suzuki, Hitomi,Takeuchi, Toyomi,Mori, Tadashi
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p. 3111 - 3115
(2007/10/03)
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