Experimental and Theoretical Studies of the Gas-Phase Kinetics of Epichlorohydrin with Tropospheric Oxidants

The rate coefficient of the gas-phasereaction of epichlorohydrinwith the OH radical is measured by both absolute and relative ratemethods. The absolute rate coefficient is found to be (3.81 & PLUSMN;0.33) x 10(-13) cm(3) molecule(-1) s(-1) and the average relative rate coefficientis found to be (3.72 & PLUSMN; 1.06) x 10(-13) cm(3) molecule(-1) s(-1) using1,2-dichloroethane and ethane as reference molecules. Over the temperaturerange of 258-333 K, the rate coefficient of epichlorohydrinand OH reaction decreases exponentially with decreasing temperature.The relative rate coefficient of the reaction of epichlorohydrin withthe Cl atom is measured to be (4.22 & PLUSMN; 0.65) x 10(-12) cm(3) molecule(-1) s(-1) using 1,2-dichloroethane as the reference molecule. The net troposphericlifetime of epichlorohydrin is calculated to be about 4 weeks. Thelifetime reduces to nearly half near the marine boundary layer wherethe Cl reaction becomes more prominent than the OH reaction. Formicacid and acetic acid are found to be the major degradation productsin the reaction of epichlorohydrin with OH radical, while formic acidand 1,3-dichloropropan-2-one are found to be major products in thereaction of epichlorohydrin with Cl atom. The theoretical OH ratecoefficient using transition-state theory with the Wigner tunnelingcorrection was calculated to be 1.71 x 10(-13) cm(3) molecule(-1) s(-1) at 298 K. A good agreement for the activation energy was obtainedbetween theory (6.8 kJ/mol) and experiment (& SIM;9 kJ/mol). Theozone-creation potential of epichlorohydrin and its global warmingpotential are determined. Structure-reactivity relationshipis discussed in the context of ring size, cyclic and acyclic ethers.