Ethane excited, decomposition

The photolysis of trifluoroacetone with light of wavelength 3130 A. has been studied by Sieger and Calvert.48 The products of decomposition were shown to be carbon monoxide, methane, ethane, 1,1,1-trifluoro-ethane, and hexafluoroethane. There was no indication of the presence of carbon tetrafluoride or methyl fluoride. The quantum yield of all products was low at low temperature and it is assumed that the excited molecule of trifluoroacetone has an appreciable lifetime and may be deactivated by collision before decomposition can occur. This contention is supported by the decrease in the quantum yields observed when foreign gases such as carbon dioxide are added, and by the fall in quantum yields with increase in trifluoroacetone concentration. 

Vanpee and Grard133 made a quantitative study of the formation of saturates (mainly ethane) in the photolysis of CH2CO with added methane (ratios CH4/CH2CO = 1 to 7) at 28 to 250 °C. and found that the results could be explained by a mechanism involving competition between CH4 and CH2CO for methylene by reactions of the first order in methylene. The rate of reaction of CH2 with CH4 was found to be 0.183 that of the reaction with ketene. Decomposition of excited ethane by the reaction... 

Acetylene is a constant fraction of the photolysis product at 1236 A for a given pressure of ethane, and is attributed to the decomposition of excited ethylene formed in reaction (5). Ethylene is formed both by stabilization of excited ethylene and by the primary step involving elimination of two hydrogen atoms. In the photolysis of CH3CD3, Ausloos et have observed the ratio acetylene/... 

The effect of electrical fields on the radiolysis of ethane has been examined by Ausloos et and this study has shown that excited molecules contribute a great deal to the products. The experiments were conducted in the presence of nitric oxide, and free-radical reactions were therefore suppressed. The importance of reactions (12)-(14) was clearly demonstrated by the use of various isotopic mixtures. Propane is formed exclusively by the insertion of CH2 into C2H6 and the yield is nearly equal to the yield of molecular methane from reaction (14). Acetylene is formed from a neutral excited ethane, probably via a hot ethylidene radical. Butene and a fraction of the propene arise from ion precursors while n-butane appears to be formed both by ionic reactions and by the combination of ethyl radicals. The decomposition of excited ethane to give methyl radicals, reaction (15), has been shown by Yang and Gant °° to be relatively unimportant. The importance of molecular hydrogen elimination has been shown in several studies ° °. ... 

Sieger and Calvert reported the photolysis products of 1,1,1-trifluoroacetone at A 3130 A to be carbon monoxide, methane, ethane, 1,1,1-trifluoroethane, and hexafluoroethane. A low quantum yield for decomposition near room temperature may be explained in terms of the excited trifluoroacetone having an appreciable lifetime and therefore suffering possible collisional deactivation before decomposition can occur. Two possible primary stepts of Type 1 have been proposed... 

Recent investigations on ethane formation in the photolysis of acetaldehyde indicate that decomposition into methyl and formyl radicals occurs from the triplet state which is also removed by first-order internal conversion and, to some extent, by second-order deactivation. In the mercury-photosensitized reaction methyl radicals are formed by direct dissociation of the excited aldehyde molecules, as well as by collision of excited mercury atoms . 

Growcock et al. determined the decomposition rate constant for vibration-ally excited ethane produced by chemical activation, C2H6 -> 2CH3.38 The... 

Multiphoton infrared excitation of the sulfoxide stretching chromophore (ca. 1100 cm ) of DMSO also leads to production of CH3 and SO in their respective electronic ground states [120]. The direct formation of ethane was once again eliminated, this time by product analysis from double label experiments with DMSO and its Dg isotopomer. Time resolved detection of IR absorptions was used to analyze products. Though, once again, CHjSO- was not directly observed, these authors favor a stepwise decomposition because of a nonthermal rotational level distribution of the SO fragment. 

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