Rate constants of OH radical reactions in gas phase with some fluorinated compounds: A correlation with molecular parameters

For a number of hydrofluorocarbons (HFCs), E_He^z has been found to have a linear correlation with each of the following: (i) log (k/n); (ii) A/n; and (iii) E_a/R, where E_H = HOMO energy of the molecule, z = average fractional positive charge on the abstractable hydrogen atom in the molecule, k = rate constant of the gas-phase H abstraction reaction of the molecule with OH radical at 298 K, n = number of abstractable H atoms in the molecule, A = preexponential factor, and E_a/R = activation temperature of the said reaction. These correlations have been used to estimate the temperature dependent rate constants for the reactions of OH radical with CF₃CF₂CH₂CH₂CF₂CF₃, CF₃CH₂CF₂CH₂CF₃, CF₃CF₂CH₂CH₂F, CF₃CH₂CH₃, CF₃CH₂CHF₂, CF₃CHFCH₂F, and CHF₂CHFCHF₂ as {6.97 × 10⁻¹³ exp(1481/T)}, {5.43 × 10⁻¹³ exp(1754/T)}, {7.95 × 10⁻¹³ exp(l308/T)}, {8.0 × 10⁻¹³ exp(1300/T)}, {7.03 × 10⁻¹³ exp(1470/T)}, {7.33 × 10⁻¹³ exp(1417/T)}, and {8.09 × 10⁻¹³ exp(1285/T)}, respectively. These have not yet been measured experimentally. Linear correlation between E_He^z and log (k/n) has also been observed for nine halogen substituted acetaldehydes. On the other hand, E_H is found to have a better linear correlation with log (k/n) than E_He^z in the case of fluorinated ethers and alcohols where the available experimental data are at present limited. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 187–194, 1997.