Reactions of alkoxy and alkyl peroxy radicals

Sensitizing effects of NOx on CH4 oxidation at high pressure

“…The high-pressure limiting rate constant for NO 2 + C 2 H 5 O C 2 H 5 ONO 2 (R25) was characterized experimentally by Frost and Smith [94] at 295 K and 2-130 mbar of He, yielding k 25,∞ = (1.7 ± 0.2) × 10 13 cm 3 /mol s. This is in reasonable agreement with the recommended value of 2.5 × 10 13 cm 3 /mol s from the review of Batt [102], based on unpublished data. Batt further advocated the branching ratio k 24 /k 25,∞ = 0.1 for the bimolecular channel.…”

“…Their recommendation is followed in the present work, including an estimated center-broadening factor of F cent,25 = 0.6, identical to the analogous reaction between NO 2 and CH 3 O discussed above. The rate coefficient for the bimolecular channel to HONO + CH 3 CHO (R24) has been obtained from the branching ratio proposed by Batt [102] using the constant value of k 25,∞ from Frost and Smith [94]. The resulting value of k 24 is consistent with the rate constant for the corresponding bimolecular channel from NO 2 + CH 3 O.…”

Reactions of alkoxy radicals under atmospheric conditions: The relative importance of decomposition versus reaction with O2

“…Thus, the present and previous methods predict that decomposition by H-atom elimination [for which A(AH) = 48.6 kcal mo1-1 (as shown for the CH30 radical)] does not compete with the 02 reaction or with Cl-atom elimination (Batt, 1987;Rayez et al, 1987;Atldnson, 1990b). In agreement with theoretical calculations (Rayez et al, 1987), the present correlation predicts that the CHCI20 radical reacts by C1 atom decomposition rather than by reaction with 02, as observed (Niki et aL, 1980), while the CH2CIO radical is expected to react with 02 rather than decompose, as also observed (Niki et al, 1980).…”

The thermochemistry of polyoxides and polyoxy radicals

“…The geometry and heat of formation previously reported 1421 for the Jahn-Teller distorted methoxy radical CH30' are for the A state in C, symmetry; the A' state is now found to be of lower energy. However, a t -0.8 kJ mol-', the heat of formation is underestimated relative to the experimental value of 17.0 t 1.0 k J mol-' [25]. The ground state of CH,O, is of A" symmetry in the C, point group; its heat of formation is also underestimated by the MNDO half-electron method, giving a value of -18.8 kJ mo1-I as compared with Slagle and Gutman's recent experimental value of 11.3 2 3.3 kJ mol-' [241.…”