75466-08-9Relevant articles and documents
Dynamics of the gas-phase reactions of chloride ion with fluoromethane: High excess translational activation energy for an endothermic SN2 reaction
Angel, Laurence A.,Garcia, Sandra P.,Ervin, Kent M.
, p. 336 - 345 (2002)
Guided ion beam tandem mass spectrometry techniques are used to examine the competing product channels in the reaction of Cl- with CH3F in the center-of-mass collision energy range 0.05-27 eV. Four anionic reaction products are detected: F-, CH2Cl-, FCl- and CHCl-. The endothermic SN2 reaction Cl- + CH3F → CH3Cl + F- has an energy threshold of E0 = 181 ± 14 kJ/mol, exhibiting a 52 ± 16 kJ/mol effective barrier in excess of the reaction endothermicity. The potential energy of the SN2 transition state is well below the energy of the products. Dynamical impedances to the activation of the SN2 reaction are discussed, including angular momentum constraints, orientational effects, and the inefficiency of translational energy in promoting the reaction. The fluorine abstraction reaction to form CH3 + FCl- exhibits a 146 ± 33 kJ/mol effective barrier above the reaction endothermicity. Direct proton transfer to form HCl is highly inefficient, but HF elimination is observed above 268 ± 95 kJ/mol. Potential energy surfaces for the reactions are calculated using the CCSD(T)/aug-cc-pVDZ and HF/6-31+G(d) methods and used to interpret the dynamics.
