Kinetics of the Reaction between Acetyl Iodide and HI and the Heat of Formation of the Acetyl Radical

The kinetics of the gas-phase reactionCH3COI+HI⇄CH3CHO+I2has been studied in the temperature range 222°—268°C and the pressure region of about 80 mm Hg. The rate data are consistent with an I-atom, catalyzed path similar to that found for the reaction of alkyl iodides with HI. Specific rate constants and Arrhenius parameters of all the individual reaction steps are evaluated. The bond-dissociation energy of the C–I bond in AcI is found to be D (Ac–I) = 50.6 kcal and the standard heat of formation of the acetyl radical ΔHf0 (Ac) = −6.3 kcal, in excellent agreement with independent work.