The reactions of O(³P) with some carboxylic acids and esters

Abstract

The reactions of o(~P) with formic acid, acetic acid, methyl acetate, ethyl acetate, n-propyl acetate, and isopropyl acetate have been studied kinetically as a function of temperature. The rate constants were measured in a discharge-flow system under pseudo-first-order conditions with a large excess of the organic reagent. No reaction could be found between o(~P) and either formic acid or acetic acid in the temperature range 300-420 K. The acetate esters, on the other hand, reacted with 0c3P) at readily measurable rates over the same temperature range. The temperature dependence of the rate constants for these reactions in the temperature range 300-580 K is given, in the units L mol-' s-I, by: Le fait qu'il ne se produise pas de rCactions a des vitesses mesurables avec les acides carboxyliques, qu'il y a une augmentation systCmatique dans le facteur prkexponentiel avec l'augmentation du groupe ester et que l'on observe la formation d'acide acCtique avec un rendement significatif parmi les produits des rCactions avec les esters indique que l'attaque par o(~P) se fait surtout au niveau de la fonction ester. On a utilisC des corrClations linCaires d'Cnergie libre pour comparer les resultats pour les esters avec ceux pour des rCactions de o(~P) avec d'autres composts organiques contenant de l'oxygkne.Mots clis : cinetique, mecanisme, rtactions du o(~P) avec les esters.

Ab Initio Kinetics of Hydrogen Abstraction from Methyl Acetate by Hydrogen, Methyl, Oxygen, Hydroxyl, and Hydroperoxy Radicals

“…(a) and (b) compare the two H-abstractions from MA by O atom. Figure (c) depicts the total rate constants for the two reactions and compares them with two sets of experimental rate coefficients by Caravan et al (green triangles) and Mix et al­(blue crosses).…”

“…Similarly, MRACPF2 predicts larger barrier heights than CCSD­(T) for MA + O, and hence the rate constants with MRACPF2 energies are lower for both reactions A and B, as depicted in Figure (a and b). Caravan et al (green triangles) and Mix et al (blue crosses) measured the total rate constants of MA + O ( 3 P ) in a discharge-flow system over the ranges 300–420 K and 300–430 K, respectively. Caravan et al concluded that the main contribution was H-abstraction by an O atom, especially from the OCH 3 group of MA.…”

“…Caravan et al (green triangles) and Mix et al (blue crosses) measured the total rate constants of MA + O ( 3 P ) in a discharge-flow system over the ranges 300–420 K and 300–430 K, respectively. Caravan et al concluded that the main contribution was H-abstraction by an O atom, especially from the OCH 3 group of MA. The computed total abstraction rates are compared with these experimental values in Figure (c).…”

“…Arthur and Newitt, 19 and Ferguson and Pearson 20 both measured rate constants for H-abstraction from MA by CH 3 at low temperature. Peukert et al 21 computed the rate constants for H-abstraction from MA by H and CH 3 and also obtained the experimentally derived coefficients for abstraction by H in the temperature range 1222−1313 K. Caravan et al 22 and Mix et al 23 studied the total consumption rates of MA by O( 3 P) in an O atom-rich environment and concluded that the abstraction reactions contributed most to the total rates. Most of these experiments were conducted over small temperature ranges and could not measure the branching ratio of the two Habstraction channels from the two methyl groups in MA, which largely determines the product distributions from combustion.…”

Non-thermal plasma based decomposition of volatile organic compounds in industrial exhaust gases

“…In the case of ethyl acetate, the presence of humidity improved the removal efficacy significantly. The positive effect of humidity was explained by the production of OH radicals which have higher rate constants for the reaction with ethyl acetate compared to O radicals [*1.5 9 10 -12 and *5 9 10 -15 cm 3 molecule -1 s -1 , respectively (Picquet et al 1998;Caravan et al 1996)]. In fact, Rudolph et al suggested that in dry air, the excited states of N 2 play a more important role than O radicals in the decomposition of ethyl acetate.…”