Competitive αα- and αβ-dehydrohalogenations from CH₃CDF₂behind shock waves

Abstract

An estimate of the extent of the aa-elimination of H F in 1,l-difluoroethane is obtained from a study of the shock-tube pyrolysis of the deuteriated isomer, CH3CDF,

Fluorinated Carbenes

“…425,426 The deuterated analog has also been produced in the decomposition of chemically activated CD 3 CHF 2 and detected as the rearrangement product alkene, CD 2 CDF. 426,427 It was concluded by Kim et al that the R,R-elimination pathway accounted for 10% of the total elimination in CH 3 CHF 2 , 426 whereas a value of 13% was found by Sekhar et al 425 In addition, the activation energy toward 1,2-hydrogen migration in fluoro(methyl)carbene was calculated as 21 kcal/mol using the MP4/ 6-31G** basis set on MP2/6-31G*-optimized geometries. 420 Evanseck and Houk predicted an activation barrier of 19 kcal/mol, obtained by correcting the value of Dailey by 0.9 kcal/mol (difference between the MP2/6-311G** and MP2/6-31G** values for methylcarbene) and also correcting for the zero point energy (0.9 kcal/mol).…”

“…Irradiation (λ > 475 nm) of 420 in a 0.5-4% O 2 doped argon matrix produced 421 and the oxidation products trifluoroacetophenone (425) and phenyl trifluoroacetate (427). 514 The ratio of carbene to oxidation products was dependent on the O 2 matrix content.…”

“…Fluoro(methyl)carbene ( 196 ) has been generated by the α,α elimination of DF from CH 3 CDF 2 or HF from CH 3 CHF 2 and detected as the 1,2-hydrogen migration product 197 (eq 103). , The deuterated analog has also been produced in the decomposition of chemically activated CD 3 CHF 2 and detected as the rearrangement product alkene, CD 2 CDF. , It was concluded by Kim et al that the α,α-elimination pathway accounted for 10% of the total elimination in CH 3 CHF 2 , whereas a value of 13% was found by Sekhar et al In addition, the activation energy toward 1,2-hydrogen migration in fluoro(methyl)carbene was calculated as 21 kcal/mol using the MP4/6-31G** basis set on MP2/6-31G*-optimized geometries . Evanseck and Houk predicted an activation barrier of 19 kcal/mol, obtained by correcting the value of Dailey by 0.9 kcal/mol (difference between the MP2/6-311G** and MP2/6-31G** values for methylcarbene) and also correcting for the zero point energy (0.9 kcal/mol) …”

Infrared laser multiphoton dissociation of 1,2-dichloro-1,1-difluoroethane (CF2ClCH2Cl)

“…(37) P. A. A**products (23) where A** denotes activated molecules with an internal energy content augmented by V-V energy transfer to above the critical energy. For reaction 21 to be feasible requires a high population of A* molecules, which is not unreasonable at the photon densities in the laser beam.…”