2268-32-8Relevant articles and documents
Organocatalytic C?F Bond Activation with Alanes
Jaeger, Alma D.,Ehm, Christian,Lentz, Dieter
supporting information, p. 6769 - 6777 (2018/04/02)
Hydrodefluorination reactions (HDF) of per- and polyfluorinated olefins and arenes by cheap aluminum alkyl hydrides in non-coordinating solvents can be catalyzed by O and N donors. TONs with respect to the organocatalysts of up to 87 have been observed. Depending on substrate and concentration, high selectivities can be achieved. For the prototypical hexafluoropropene, however, low selectivities are observed (E/Z≈2). DFT studies show that the preferred HDF mechanism for this substrate in the presence of donor solvents proceeds from the dimer Me4Al2(μ-H)2?THF by nucleophilic vinylic substitution (SNV)-like transition states with low selectivity and without formation of an intermediate, not via hydrometallation or σ-bond metathesis. In the absence of donor solvents, hydrometallation is preferred but this is associated with inaccessibly high activation barriers at low temperatures. Donor solvents activate the aluminum hydride bond, lower the barrier for HDF significantly, and switch the product preference from Z to E. The exact nature of the donor has only a minimal influence on the selectivity at low concentrations, as the donor is located far away from the active center in the transition states. The mechanism changes at higher donor concentrations and proceeds from Me2AlH?THF via SNV and formation of a stable intermediate, from which elimination is unselective, which results in a loss of selectivity.
CO2 Laser-induced Decomposition of 1,2-Dichloro-1-fluoroethane
Ogura, Hiroo,Yano, Takayuki
, p. 1239 - 1250 (2007/10/02)
CH2ClCHFCl was photolyzed with a TEA CO2 laser at 1033.5 cm-1.The infrared multiphoton dissociation mechanism of CH2ClCHFCl was investigated under various conditions: Sample gas pressure, additive gas presure, pulse number, pulse energy, and pulse duration.It is concluded that primary process of the IRMPD is direct eleimination of molecular HCl and HF, HCl elimination being predominant channel.Primary HCl elimination products cis-and trans-CHF=CHCl, and CH2=CFCl are formed at high vibrational levels, from which additional photon absorption occures in the secondary photolysis to give rise to CH=CCl, CH=CF, and CH2=CHF.All of the secondary products are concluded to be derived from mainly CH2=CFCl among the chlorofluoroethene isomers.CH2=CFCl decomposes via HF and HCl elimination channels together with the C-Cl bond repture channel. appears to be generated by the H atom abstraction reaction of C2H. radical, which may result from further decomposition of and/or .The neat IRMPD at higher pressures gives quite similar primary product distribution, but markedly different secondary product distribution from those in shock tube pyrolysis.
