Photochemistry of the Fluoro Ketones. 1,1,3,3-Tetrafluoroacetone 1

Self Cite

Section: Methodsmentioning

confidence: 99%

“…Calibrations were made with commercially available samples, except for C2F4Hz and C4F2H8. The former was prepared by prolonged photolysis of the TFA and separated by low-temperature fractionation from the fluoroproducts [3], which comprised CF2H2, the C2F4H2, and small amounts of 1,1,2,2,3,3-hexafluoropropane (C3F6Hz) [l].…”

Section: Methodsmentioning

confidence: 99%

Disproportionation reactions between alkyl and fluoroalkyl radicals. VI. Difluoromethyl and n‐propyl radicals

Pritchard

Abbas

Piasecki

et al. 1991

Self Cite

“…Purified samples of 1,1,3,3-tetrafluoroacetone (TFA) and 1,1,3,3-tetrafluoracetone-de (TFAD) were used as photolytic sources of CF2H and CF2D radicals [22,27]. Ethyl radicals were generated from the photolysis of azoethane (AE), diethylketone (DEK), and propionaldehyde (PrA), respectively.…”

Section: Experimental and Resultsmentioning

confidence: 99%

“…The photolysis system and analytical gas-handling procedures have been described previously [22,24]. The reaction cell volume was 156 mL in all experiments.…”

Section: Experimental and Resultsmentioning

confidence: 99%

Disproportionation reactions between CF₂H and C₂H₅ radicals in the gas phase

Nilsson¹,

Pritchard²

1982

“…The Arrhenius parameters are compared with previous determinations in Table 11. The initial results of Pritchard and Bryant [7] (E8 = 6.9 kcal/mole and log A s = 10.4 (mole-' cc sec-l)) were later thought to be subject to unknown uncertainties owing to suspected impurities in the TFA [6], and consequently they can be neglected in relation to the present discussion. The reaction scheme for the photolysis of DFA is extended to include the hydrogen abstraction reaction The corrections to the yields of CHzFz to allow for reaction (8) were calculated from our Arrhenius equation for ks/k7I/'.…”

Section: A the Photolyses Of Dfa And Tfa Alonementioning

confidence: 99%

Hydrogen abstraction from organosilicon compounds. The reactions of fluoromethyl radicals with tetramethylsilane. Polar effects in gas phase reactions

Kerr

Timlin

1971

The photolysis of 1,1,3,3-tetrafluoroacetone has been reinvestigated as a source of CHFz radicals at temperatures up to 578'K, and the following rate constant ratio was determined for the reactions (8) (7)2CHF2 -+ CHFzCHFz* CHFz + CHFzCOCHFz -+ CHzFz + CF~COCHFZ log (k~/k~1'2)(mole-1'zcc1'2sec-1'2) = (4.73 f 0.18) -(11.26 f 0.40)/8* 1,l-Difluoro-and 1,1,3,3-tetrafluoroacetone were photolyzed in the presence of tetramethylsilane, and Arrhenius parameters were measured for the hydrogen abstraction re- By comparing with previous data on the CH3 and CF, reactions, the activation energies were interpreted in terms of the enthalpy changes for the reactions and a polar effect operative between the attacking fluoromethyl radicals and the substrate which tends to reduce the activation energy progressively as the fluorine content of the radical increases. This polar effect, which decreases the activation energy for hydrogen abstraction from SiMed along the series CH3, CHzF, CHFs, and CF3, is in marked contrast to the polar repulsion between the fluorinated radicals and SiHCls which was tentatively proposed to explain the increase in activation energy observed in the same series of reactions with SiHC13.* 8 = 2.303 RT in kcal/rnole. 69