Experimental and theoretical investigations on the photo-oxidation reaction of OH radicals with 2,3-dimethyl-1,3-butadiene in gas phase

209-218The temperature dependent rate coefficients have been measured for the reaction of OH radicals with 2,3-dimethyl-1,3-butadiene with reference to isoprene over the temperature range of 269-359K. Gas chromatography has been used to measure the concentrations of the organics. The measured rate coefficient is k = (1.01±0.1)×10−10 cm3molecule−1s−1 at 298K and 760 Torr. The derived Arrhenius expression is k269-359K = (6.67±3.84)×10−12exp[(807±89)/T] cm3molecule−1s−1 over the studied temperature range. To understand the reaction mechanism and to continue our earlier study of 2,3-dimethyl-1,3-butadiene with Cl atoms, computational calculations have been performed over the temperature range of 275-400K. Temperature dependent rate coefficients have been calculated using CVT/SCT (Canonical Variational Transition state theory with Small Curvature Tunneling) in combination with CCSD(T)/aug-cc-pvdz//M062X/6-311+G(d,p) level of theory. To understand the atmospheric implications of butadienes, the obtained rate coefficients have been compared with 1,3-butadiene and 2-methyl-1,3-butadiene (isoprene). Atmospheric lifetimes and global warming potentials of these butadienes are discussed