Reaction kinetics of Cl atoms with limonene: An experimental and theoretical study

Abstract

Rate coefficients for the reaction of Cl atoms with limonene (C10H16) were measured between 278–350 K and 800 Torr of N2, using the relative rate technique, with 1,3-butadiene (C4H6), n-nonane (C9H20), and 1-pentene (C5H10) as reference compounds. Cl atoms were generated by UV photolysis of oxalyl chloride ((COCl)2) at 254 nm. A gas chromatograph equipped with a flame ionization detector (GC-FID) was used for quantitative analysis of the organics. The rate coefficient for the reaction of Cl atoms with limonene at 298 K was measured to be (8.65 ± 2.44) × 10−10 cm3 molecule−1 s−1. The rate coefficient is an average value of the measurements, with two standard deviations as the quoted error, including uncertainties in the reference rate coefficients. The kinetic data obtained over the temperature range of 278–350 K were used to derive the following Arrhenius expression: k(T) = (9.75 ± 4.1) × 10−11 exp[(655 ± 133)/T] cm3 molecule−1 s−1. Theoretical kinetic calculations were also performed for the title reaction using conventional transition state theory (CTST) in combination with G3(MP2) theory between 275 and 400 K. The kinetic data obtained over the temperature range of 275–400 K were used to derive an Arrhenius expression: k(T) = (7.92 ± 0.82) × 10−13 exp[(2310 ± 34)/T] cm3 molecule−1 s−1. The addition channels contributes maximum to the total reaction and H-abstraction channels can be neglected in the range of studied pressures. The Atmospheric lifetime (τ) of limonene due to its reaction with Cl atoms was estimated and concluded that the reaction with chlorine atoms can be an effective tropospheric loss pathway in the marine boundary layer and in coastal urban areas.