Photosensitized Reactions of Carbon Tetrafluoride

Abstract

Hg (63P1) at room temperature and at 300 °C. and Hg (61P1) at room temperature fail to react with carbon tetrafluoride at a measurable rate. Xe (3P1) causes carbon tetrafluoride to decompose with a quantum efficiency of about unity to yield fluorine and an unidentified solid product. It is concluded that the energy necessary to break the first C–F bond m CF4 is more than 154 and less than 194 kcal. per mole. Hydrogen atoms produced from Hg (63P1) at room temperature and at 300 °C. and from Hg (61P1) at room temperature do not react with carbon tetrafluoride. It is concluded from this that the activation energy of the reaction CF4 + H → CF3 + HF is not less than 14 kcal. per mole.

Ionization and dissociation of the trifluoromethyl halides by electron impact

“…R ecent estimates of t he di ssociation energy D (CF3-F ) range from 1] 6 kcal [12] to 195 kcal [21]. Luft [5], on consideration of recently published enthalpies of formation and other thermochemical data, derives a value of 138 ± 4 kcal.…”

Direct photolysis of tetrafluoroethylene at 1849 Å

“…The photolysis cell was 35 cm by 16 cm in diameter, and contained an axial low pressure mercury lamp based on the design by Dacey and Hodgins (7). The lamp, made of suprasil (Englehard Industries Inc.), was surrounded by a vacuum jacket to reduce the temperature of the surface exposed to the TFE.…”

“…It is difficult to justify exclusively a mechanism for the formation of perfluoropropane. Reactions [7] to [9] indicate a probable pathway3 3The authors are grateful to a referee for suggesting this mechanism.…”

The Formation of Trifluoromethyl Radicals in the Gas Phase

“…per mole (5). However, there is reason to suspect that the second C-F bond is quite a wealc one-that is, that the trifluoromethyl radical is thermally ~~nstable.…”

“…Since the highest estimate of the average bond energy in carbon tetrafluoride is about 123 kilocalories per mole, the strength of sollle of the bonds remai~ling-after the first fluorine atom has been I-enloved must be considerably lower. And the fact that Dacey and Hodgins (5) found no hexafluoroethane in the products of the xenon pl~otosensitized decomposition of carbon tetrafluoride indicates that it may be the CF3 radical which is unstable.…”