The 1,2-Interchange of F and Cl interconverting CH2FCD2Cl and CH2ClCD2F

Mary Kate Tucker

Abstract


CH2FCD2Cl was prepared using gas-phase recombination of CH2F and CD2Cl radicals, at 25°C with an internal energy of 91 kcal mol-1. Three unimolecular processes compete with collisional deactivation: HCl and DF elimination to give CHF=CD2 and CH2=CDCl and isomerization of CH2FCD2Cl to give CH2ClCD2F by means of halogen interchange. The formation of CHCl=CD2, via HF elimination from CH2ClCD2F, was observed and a rate constant was assigned for the interchange reaction. Previous publications on chemically activated CH2ClCH2F, along with this current study allow the designation of the three unimolecular rate constants. The halogen rearrangement has a branching ratio of 0.25 ± 0.05. When compared, the experimental rate constant along with the rate constant calculated using Rice Rasmburger Kassel Marcus (RRKM) theory produces a threshold energy of 59 ± 2 kcal mol-1 for this type 1 dyotropic rearrangement. All three unimolecular processes have similar threshold energies. CD2ClCD2Cl and CH2FCH2F molecules are also generated from the radical recombination reactions, and the rate constants for DCl and HF elimination were measured in order to confirm that reliable data for CH2FCD2Cl was obtained from the photolysis of CD2ClI and (CH2F)2CO.


Keywords


Hydrochlorofluorocarbons; Interchange; Rate

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