- Matrix-isolation and ab initio molecular orbital study of 2,2,2-trifluoroethylidene
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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.
- O'Gara, John E.,Dailey, William P.
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p. 12016 - 12021
(2007/10/03)
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- Facile conversion of trifluoroacetyltriphenylsilane 2,4,6-triisepropylbenzenesulfonylhydrazone to 2,2,2-trifluorodiazoethane. An unusual example of the Bamford-Stevens reaction
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Trifluoroacetyltriphenylsilane 2,4,6-triisepropylbenzenesulfonylhydrazone(1) reacted with dipolarophiles in the presence of Et3N to produce trifluorcmethylated pyrazoles or pyrazolines in good yields. The reaction was found to proceed through t
- Jin, Fuqiang,Xu, Yuanyao,Ma, Yiling
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p. 6161 - 6164
(2007/10/02)
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