Kj. Hsu et Wb. Demore, TEMPERATURE-DEPENDENT RATE CONSTANTS AND SUBSTITUENT EFFECTS FOR THE REACTIONS OF HYDROXYL RADICALS WITH 3 PARTIALLY FLUORINATED ETHERS, Journal of physical chemistry, 99(28), 1995, pp. 11141-11146
Rate constants and temperature dependencies for the reactions of OH wi
th CF3OCH3 (HFOC-143a), CF2HOCF2H (HFOC-134), and CF3OCF2H (HFOC-125)
were studied using a relative rate technique in the temperature range
298-393 K. The following absolute rate constants were derived: HFOC-14
3a, 1.9E-12 exp(-1555/T); HFOC-134, 1.9E-12 exp(-2006/T); HFOC-125, 4.
7E-13 exp(-2095/T). Units are cm(3) molecule(-1) s(-1). Substituent ef
fects on OH abstraction rate constants are discussed, and it is shown
that the CF3O group has an effect on the OH rate constants similar to
that of a fluorine atom. The effects are related to changes in the C-H
bond energies of the reactants (and thereby the activation energies)
rather than changes in the preexponential factors. On the basis of a c
orrelation of rate constants with bond energies, the respective D(C-H)
bond strengths in the three ethers are found to be 102, 104, and 106
kcal/mol, with an uncertainty of about 1 kcal/mol.