Rate coefficients for the reactions of hydroxyl radicals with a series of cyclic ethers and aliphatic diethers have been determined at 298 ± 2 K. Experiments were performed using a photolytic relative rate method at atmospheric pressure and the absolute rate technique of pulsed laser photolysis−laser induced fluorescence. The temperature dependence of the rate coefficients for the cyclic ethers was also studied over the temperature range 263−372 K. The rate coefficients show significant deviations from simple structure−activity relationships. The reactivity of the aliphatic diethers toward hydroxyl radicals is discussed in terms of the initial formation of a hydrogen-bonded adduct which then undergoes an intramolecular H atom transfer via five-, six-, and seven-membered-ring structures. The reactivity of cyclic ethers is also discussed in relation to adduct formation. However, because of steric restrictions, it is unlikely that the hydrogen-bonded adducts readily undergo H atom transfer via ring formation.

In Table 1, the reference compound used for 1,3dioxepane was in fact (CH 3 ) 2 CHOCH 2 CH 2 OH and not (CH 3 ) 2 -CH(OH)CH 2 OCH 3 . The rate coefficient for reaction of OH with (CH 3 ) 2 CHOCH 2 CH 2 OH (k 5 ) was 21.0 × 10 -12 cm 3 molecule -1 s -1 , as reported by Porter et al. 2 The reported value of k 4 /k 5 for 1,3-dioxepane, 0.58

The products of the hydroxyl (OH) radical and chlorine (Cl) atom initiated oxidation of 1,3-dioxane are determined under various reaction conditions in a 50 L teflon reaction chamber using FTIR spectroscopy for analysis. The major products detected in all experiments are (2-oxoethoxy)methyl formate, formic acid and methylene glycol diformate with average molar yields of 0.50±0.05, 0.41±0.02 and 0.03±0.01 respectively for the OH initiated oxidation in the presence of NO(x). The yields of these products do not vary significantly with O(2) partial pressure or oxidising agent (OH or Cl). However, the yield of formic acid decreased by at least a factor of two in the absence of NO(x). The results of these experiments are used to elucidate a simplified gas-phase atmospheric degradation scheme for 1,3-dioxane and also provide valuable information on the atmospheric fate of the cyclic and linear alkoxy radicals produced in these and similar reactions. The available experimental data suggests that the relative importance of the competing pathways (reaction with O(2) and ring opening by C-C or C-O bond fission) is a strong function of the ring strain in the cycloalkoxy radicals.