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(H)e(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 ato m in the molecule, ri = rate constant of the gas-phase H abstraction r eaction of the molecule with OH radical at 298 K, n = number of abstra ctable 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 th e reactions of OH radical with CF3CF2CH2CH2CF2CF3, CF3CH2CF2CH2CF3, CF 3CF2CH2CH2F, CF3CH2CH3, CF3CH2CHF2, CF(3)CHFCH(2)E and CHF2CHFCHF2 as {6.97 x 10(-13) exp(1481/T)}, {5.43 x 10(-13) exp(1754/T)}, {7.95 x 10 (-13) exp(1308/T)}, {8.0 x 10(-13) exp(1300/T)}, {7.03 x 10(-13) exp(1 470/T)}, {7.33 x 10(-13) exp(1417/T)}, and {8.09 x 10(-13) exp(1285/T) }, respectively. These have not yet been measured experimentally. Line ar correlation between E(H)e(z) and log (k/n) has also been observed f or nine halogen substituted acetaldehydes. On the other hand, E(H) is found to have a better linear correlation with log (k/n) than E(H)e(z) in the case of fluorinated ethers and alcohols where the available ex perimental data are at present limited. (C) 1997 John Wiley & Sons, In c.