ESTIMATION OF HYDROXYL RADICAL REACTION-RATE CONSTANTS FOR GAS-PHASE ORGANIC-COMPOUNDS USING A STRUCTURE-REACTIVITY RELATIONSHIP - AN UPDATE

The structure-reactivity approach proposed by Atkinson (1986, Chem. Re v. 86, 69-201) and extended by Atkinson (1987, Int. J. Chern. Kinet. 1 9, 799-828) for the calculation df rate constants for the gas-phase re actions of the OH radical with organic compounds has been re-investiga ted using the presently available database. Substituent group factors for several new groups are derived, including those for fluorinated et hers. Using a large fraction of the available database to derive the p arameters needed to calculate the OH radical reaction rate constants, the 298 K rate constants of similar to 90% of approximately 485 organi c compounds are predicted to within a factor of 2 of the experimental values. Disagreements between calculated and experimental rate constan ts most commonly occur for halogen-containing compounds, and in partic ular for haloalkanes, haloalkenes and halogenated ethers. Disagreement s also arise for ethers, especially for polyethers and cycloethers. Th e present estimation technique is reasonably reliable when used within the database used in its derivation, but extrapolation to organic com pounds outside of this database results in a lack of assurance of its reliability, and its use for organic compounds which belong to classes other than those used in its development is discouraged.