Abstract
Alkoxy radicals represent a critical branching point in the atmospheric oxidation of volatile organic compounds. The competition among reaction with O2, isomerization reactions, and scission reactions influences ozone formation in polluted air. Reaction mechanisms are well understood, but major gaps exist in our knowledge of the branching ratios that governs the competition between various reaction pathways. Our knowledge is satisfactory for alkoxy radicals derived from alkanes, but mostly only at room temperature. Rate constants for isomerization and scission reaction will decrease dramatically between room temperature and the temperatures of the middle and upper troposphere, but the extents of these decreases are not generally known. Theoretical calculations indicate that functional groups dramatically change the rate constants for isomerization and scission; unfortunately, there is almost no experimental data available to quantify the influence of these groups on reaction rate constants.