1511-62-2Relevant articles and documents
Infrared Multiphoton Dissociation of Heptafluoropropane
Kato, Shuji,Makide, Yoshihiro,Tominaga, Takeshi,Takeuchi, Kazuo
, p. 4278 - 4284 (1987)
The dissociation yield and branching ratio in CO2-laser-induced multiphoton dissociation (MPD) of CF3CF2CHF2 were studied as a function of irradiation frequency (979.7, 1037.4, and 1081.1 cm-1) and laser fluence (focal fluence 2).Br2 was successfully employed to reveal the dissociation mechanisms by scavenging a number of primary and secondary dissociation fragments produced in the MPD.At low laser fluences the distributions of scavenged products were the same regardless of irradiation frequencies.The primary dissociation of CF3CF2CHF2 was found to proceed mainly via the higher activation energy channels (i.e., C-C ruptures: CF3CF2CHF2 -> C2F5 + CHF2, and CF3CF2CHF2 -> CF3 + C2HF4) rather than via HF elimination (CF3CF2CHF2 -> C3F6 + HF) in our experimental conditions.The observed branching ratio between the two C-C rupture channels (ca. 2:1) agreed with the results obtained by RRKM calculation.A remarkable difference in product distribution with respect to the irradiation frequency was observed at higher laser fluences.This indicates that the secondary photolysis of primarily produced radicals within the laser pulse occured significantly at higher fluences (i.e., C2F5 -> CF3 + CF2, CHF2 -> CF2 + H, CF3 -> CF2 + F, and C2HF4 -> CF2 + CHF2), depending strongly upon the irradiation frequencies.
Fluorinated phosphonium ylides: Versatile in situ Wittig intermediates in the synthesis of hydrofluorocarbons
Bhadury, Pinaki S.,Palit, Meehir,Sharma, Mamta,Raza, Syed K.,Jaiswal, Devendra K.
, p. 75 - 80 (2002)
A simple and convenient technique has been developed for the synthesis, characterisation and isolation of hydrofluoro/hydrohalofluorocarbons such as chlorodifluoromethane (CF2ClH), difluoromethane (CF2H2), bromodifluoromethane (CF2BrH) and dibromofluoromethane (CFBr2H) as possible chlorofluorocarbon (CFC) alternatives. The Wittig reaction of carbonyl compounds with in situ generated triphenylphosphonium ylides in DMF forms terminal fluoroolefins. However, in the absence of the carbonyl moiety these ylides undergo decomposition. The high reactivity of fluoromethylene triphenylphosphonium ylides in DMF in the absence of the carbonyl moiety has been exploited for the first time to design the synthesis of hydrofluorocarbons.
Schiemann et al.
, p. 669 (1967)
Experimental and computational studies on the gas-phase reaction of CBrF3 with hydrogen
Li, Kai,Kennedy, Eric M.,Moghtaderi, Behdad,Dlugogorski, Bogdan Z.
, p. 584 - 590 (2000)
Gas-phase hydrogen dehalogenation of halon 1301 (bromotrifluoromethane, CBrF3) has been studied experimentally in a tubular alumina reactor operating at atmospheric pressure. It is found that hydrogen can accelerate the decomposition of halon 1301 and that conversion levels of CBrF3 and H2 increase with temperature and residence time. CBrF3 conversion increases with decreasing input volume ratio of CBrF3 to H2. The species produced are a complex mixture of halogenated hydrocarbons including CHF3, CH2F2, C2HF3, C2F6, C2H2F4, C2HF5, CHBrF2, CH3Br, CH2Br2, CHBr2F, and CH2BrF in addition to HBr and HF. The production yield of CHF3, the major product, increases with temperature to 1023 K, after which CHF3 levels decrease with increasing temperature. Conversely, CHF3 selectivity decreases with increasing temperature, residence time, or input ratio of CBrF3 to H2. The initiation reaction is believed to be the rupture of the C-Br bond in CBrF3, and the radical species CF3 then reacts with H2 to produce H and CHF3. The key step in the process is the attack of H radical on CBrF3 to produce CF3 and HBr. Experimental data are compared with the model predictions, and good agreement between experimental and modeling prediction is obtained for CHF3 production. However, the existing mechanism does not predict the formation of CHBrF2, which is detected during the experimental study, and the concentrations of CH2F2 and C2F6 measured experimentally are significantly different from those predicted. Modifications to the existing NIST mechanism are suggested to improve the prediction of the quantity of these species produced. Gas-phase hydrogen dehalogenation of halon 1301 (bromotrifluoromethane, CBrF3) has been studied experimentally in a tubular alumina reactor operating at atmospheric pressure. It is found that hydrogen can accelerate the decomposition of halon 1301 and that conversion levels of CBrF3 and H2 increase with temperature and residence time. CBrF3 conversion increases with decreasing input volume ratio of CBrF3 to H2. The species produced are a complex mixture of halogenated hydrocarbons including CHF3, CH2F2, C2HF3, C2F6, C2H2F4, C2HF5, CHBrF2, CH3Br, CH2Br2, CHBr2F, and CH2BrF in addition to HBr and HF. The production yield of CHF3, the major product, increases with temperature to 1023 K, after which CHF3 levels decrease with increasing temperature. Conversely, CHF3 selectivity decreases with increasing temperature, residence time, or input ratio of CBrF3 to H2. The initiation reaction is believed to be the rupture of the C-Br bond in CBrF3, and the radical species CF3 then reacts with H2 to produce H and CHF3. The key step in the process is the attack of H radical on CBrF3 to produce CF3 and HBr. Experimental data are compared with the model predictions, and good agreement between experimental and modeling prediction is obtained for CHF3 production. However, the existing mechanism does not predict the formation of CHBrF2, which is detected during the experimental study, and the concentrations of CH2F2 and C2F6 measured experimentally are significantly different from those predicted. Modifications to the existing NIST mechanism are suggested to improve the prediction of the quantity of these species produced.
Alternative synthetic routes to hydrofluoroolefins
Yagupolskii, Yu. L.,Pavlenko,Shelyazhenko,Filatov,Kremlev,Mushta,Gerus,Peng, Sheng,Petrov,Nappa, Mario
, p. 134 - 141 (2015/11/10)
A series of hydrofluoroolefins with -CF=CH2, -CH=CHF and -CH=CF2 groups were designed and prepared via various synthetic routes, including HX or BrF elimination, Wittig-type olefination or fluorination using SF4.
