115781-19-6Relevant 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.
PROCESSES FOR PRODUCING AND COMPOSITIONS COMPRISING 2,3,3,3-TETRAFLUOROPROPENE AND/OR 1,2,3,3-TETRAFLUOROPROPENE
-
Page/Page column 19-20, (2008/12/05)
A process is disclosed for making CF3CF=CH2 or mixtures thereof with CHF=CFCHF2. The process involves contacting CCI3CF2CF3 and optionally CCI2FCF2CCIF2 with H2 in the presence of a catalyst including a catalytically effective amount of palladium supported on a support of alumina, fluorided aluminaand/or aluminum fluoride, to produce a product mixture including CH2=CFCF3 (and when CCI2FCF2CCIF2 is present, CHF=CFCHF2); recovering CH2=CFCF3 or a mixture thereof with CHF=CFCHF2 from the product mixture; and optionally, separating at least a portion of any CHF=CFCHF2 in the product mixture from the CH2=CFCF3 in the product mixture. The mole ratio of H2 to the total of CCI3CF2CF3 and CCI2FCF2CCIF2 fed to the reaction zone is between about 1 :1 and about 5:1. The present invention also provides another process for making CH2=CFCF3 Or mixtures thereof with CHF=CFCHF2 This process involves (a) reacting CCI3CF2CF3 and optionally CCI2FCF2CCIF2 with H2 in the presence of a catalytically effective amount of a hydrogenation catalyst to form CH3CF2CF3 (and when CCI2FCF2CCIF2 is present, CH2FCF2CHF2); (b) dehydrofluorinating CH3CF2CF3 and optionally any CH2FCF2CHF2 from (a) to form a product mixture including CH2=CFCF3, and if CH2FCF2CHF2 is present, CHF=CFCHF2; (c) recovering CH2=CFCF3 or a mixture thereof with CHF=CFCHF2 from the product mixture formed in (b); and optionally (d) separating at least a portion of any CHF=CFCHF2 in the product mixture formed in (b) from the CH2=CFCF3 in the product mixture formed in (b). The present invention also provides compositions involving CH2=CFCF3 and/or CHF=CFCHF2, including compositions useful as refrigerants, foam blowing agents, cleaning agents and aerosols and azeotropic compositions involving (a) CF2HCF=CFH and (b) HF.
