Gas-phase ozonolysis of β-ocimene: Temperature dependent rate coefficients and product distribution

ELIZABETH GAONA-COLMÁN, MARÍA B. BLANCO, IAN BARNES AND MARIANO A. TERUEL

ATMOSPHERIC ENVIRONMENT

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2016 vol. 147 p. 46 - 54

1352-2310

Rate coefficients for the reaction of β-ocimene with O3 molecules have been determined over the temperature range 288-311K at 750 Torr total pressure of nitrogen using the relative rate technique. The investigations were performed in a large volume reaction vessel using long-path in-situ Fourier transformed infrared (FTIR) spectroscopy to monitor the reactants and products. A value of k(β-ocimene + O3)= (3.74 ± 0.92) × 10-16 cm3 molecule-1 s-1 has been obtained for the reaction at 298 K. The temperature dependence of the reaction is best described by the Arrhenius expression k= (1.94 ± 0.02) × 10-14 exp [(-1181 ± 51)/T] cm3 molecule-1 s-1. In addition, a product study has been carried out at 298 K in 750 Torr of synthetic air and the following products with yields in molar % were observed: formaldehyde (36 ± 2), acetone (15 ± 1), methylglyoxal (9.5 ± 0.4) and hydroxyacetone (19 ± 1). The formation of formaldehyde can be explained by the addition of O3 to the C1-C2 double bond of the β-ocimene. Addition of O3 to the C6-C7 double bond leads to the formation of acetone and the CH3C∙(OO∙)CH3 biradical, which can through isomerization/stabilization form methylglyoxal (hydroperoxide channel) and hydroxyacetone. The formed products will contribute to the formation of PAN and derivatives in polluted environments and the oxidation capacity of the atmosphere.