2441-28-3Relevant academic research and scientific papers
THERMAL AND THERMOOXIDATIVE STABILITY OF OZONE-SAFE FREONS
Buravtsev, N. N.,Grigor'ev, A. S.,Kolbanovskii, Yu. A.,Ovsyannikov, A. A.
, p. 1880 - 1890 (2007/10/03)
The thermal stability of freons 134-a (CF3CH2F), 134 (CHF2CHF2), and 133-a (CF3CH2Cl) was studied experimentally by the pulsed adiabatic compression method.The conversion of the freons, beginning at a value of 0.0002, was determined from the carbon balance of the reaction products, calculated from the chromatographic data.The Arrhenius expressions for the total rate constants of thermal decomposition of the freons are presented.The intermediates of the thermal transformations of the freons were recorded by kinetic spectroscopy in the ultraviolet and visible regions.The UV spectrum of the carbene :CHCF3 with characteristic absorption maxima at λ 235 and 430 nm is described for the first time.
Matrix-isolation and ab initio molecular orbital study of 2,2,2-trifluoroethylidene
O'Gara, John E.,Dailey, William P.
, p. 12016 - 12021 (2007/10/03)
Photolysis of 2,2,2-trifluorodiazoethane (2) in an argon matrix at 12 K generates triplet 2,2,2-trifluoroethylidene (1) in addition to a significant amount of trifluoroethylene (3) and small amounts of trifluoromethyldiazirine (4). These compounds were identified by IR and UV spectroscopy. Short-wavelength - photolysis of the carbene 1 converts it to trifluoroethylene, while slowly warming the matrix to 35 K results in dimerization to the isomeric hexafluorobut-2-enes. High-level ab initio calculations (QCISD(T)6-311(2D,2P)//MP2-FC/6-31G**) are reported for the singlet and triplet states of 2,2,2-trifluoroethylidene as well as for methylene and ethylidene. The calculated IR spectrum for triplet 2,2,2-trifluoroethylidene is in good agreement with the experimental one, but the UV/vis spectrum calculated using the CIS method does not match very well. The transition structures for the 1,2-fluorine atom rearrangement of the single and triplet states of carbene 1 to trifluoroethene were calculated at the QCISD(T)-FC/6-311(2D,2P)//MP2-FC/6-31G** level of theory. The calculated barrier for 1,2-fluorine atom migration in the singlet carbene, 21.5 kcal/mol, is less than suggested by recent experimental results (29 ± 4 kcal/ mol). The calculated barrier for the corresponding rearrangement in the triplet system was 51 kcal/mol. Previous reports concerning the energies and geometries of these calculated transition structures are shown to be in error.
