Study of the Reaction Cl + Ethyl Formate at 700-950 Torr and 297 to 435 K: Product Distribution and the Kinetics of the Reaction C sub(2)H sub(5)OC(=O) arrow right CO sub(2) + C sub(2)H sub(5)

The kinetics and mechanism of the reaction of atomic chlorine with ethyl formate [Cl + CH sub(3)CH sub(2)O(C=O)H, reaction 1] have been examined. These experiments were performed at pressures of 760-950 Torr and temperatures from 297 to 435 K. Reactants and products were quantified by gas chromatography-flame ionization detector (GC/FID) analysis. The initial mixture contained ethyl formate, Cl sub(2), and N sub(2). Cl atoms were generated by UV photolysis of this initial mixture at 360 nm, which dissociates Cl sub(2). The rate constant of reaction 1 was measured at 297 K relative to that of the reaction Cl + C sub(2)H sub(5)Cl (reaction 2), yielding the rate constant ratio k sub(1)/k sub(2) = 1.09 plus or minus 0.05. The final products formed from reaction 1 are ethyl chloroformate, 1-chloroethyl formate, and 2-chloroethyl formate. These products result from the reactions with Cl sub(2) of the three free radicals formed by H atom abstraction from ethylformate in reaction 1. Based on the molar yields of these three chlorinated products, the yields of the three radicals formed from reaction 1 at 297 K are (25 plus or minus 3) mole percent of CH sub(3)CH sub(2)O(C=O); (67 plus or minus 5) mole percent of CH sub(3)CHO(C=O)H; and (8 plus or minus 2) mole percent of CH sub(2)CH sub(2)O(C=O)H. A second phase of this experiment measured the rate constant of the decarboxylation of the ethoxy carbonyl radical [CH sub(3)CH sub(2)O(C=O) arrow right CO sub(2) + C sub(2)H sub(5), reaction 4] relative to the rate constant of its reaction with Cl sub(2) [CH sub(3)CH sub(2)O(C=O) + Cl sub(2) arrow right CH sub(3)CH sub(2)O(C=O)Cl + Cl, reaction 3a]. Over the temperature range 297 to 404 K at 1 atm total pressure, this ratio can be expressed by k sub(4)/k sub(3a) = 10 super(23.56 plus or minus 0.22) e super(-(12700 plus or minus 375)/)RTmolecules cm super(-3). Estimating the value of k sub(3a) (which has not been measured) based on similar reactions, the expression k sub(4) = 5.8 10 super(12) e super(-(12700)/)RTs super(-1) is obtained. The estimated error of this rate constant is plus or minus a factor of 2 over the experimental temperature range. This rate expression is compared with recent ab initio calculations of the decarboxylation of the analogous methoxy carbonyl radical.