Absolute Rate Constants for the Gas-Phase Ozonolysis of Isoprene and Methylbutenol N. KLAWATSCH-CARRASCO, J. F. DOUSSIN, P. CARLIER LISA, Universit ´ e Paris 12, 61 avenue du G ´ en ´ eral de Gaulle, 94010 Cr ´ eteil Cedex, France Received 10 March 2003; accepted 26 September 2003 DOI 10.1002/kin.10175 ABSTRACT: The reactions of the biogenic organic compounds isoprene and 2-methyl-3- buten-2-ol (MBO) with ozone have been investigated under controlled conditions for pres- sure (atmospheric pressure) and temperature (293 ± 2 K), using FTIR spectrometry. CO was added to scavenge hydroxyl radical formation during the ozonolysis experiments. Reaction rate constants were determined by absolute rate technique, by measuring both ozone and the organic compound concentrations. The measured values were k 1 = (1.19 ± 0.09) × 10 -17 cm 3 molecule -1 s -1 for the reaction between ozone and isoprene and k 2 = (8.3 ± 1.0) × 10 -18 cm 3 molecule -1 s -1 for the reaction between ozone and MBO. C  2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 152–156, 2004 INTRODUCTION Biogenic volatile organic compounds (BVOCs) ac- count for around 90% of global hydrocarbon emissions into the Earth’s atmosphere [1]. Several thousand dif- ferent compounds have been identified, including well- known unsaturated hydrocarbons such as isoprene, and mono- and sesquiterpenes. The gas-phase degradations of these reactive molecules contribute to produce pho- tooxidants in the atmosphere. These reactions are li- able to aggravate the situations of pollution events by increasing the background level of ozone in the lower Correspondence to: N. Klawatsch-Carrasco; e-mail: klawatsch@ lisa.univ-paris12.fr. Contract grant sponsor: Institut National de l’Environnement et des RISques. c  2004 Wiley Periodicals, Inc. troposphere. A good knowledge of the mechanisms and the rate constants is necessary when describing the im- pact of these processes on air quality. One oxygenated BVOC recently detected, 2-methyl-3-buten-2-ol (MBO), seems to be emitted in large quantities by certain types of trees [2,3]. The strong similarities with isoprene (structure, types of vegetation source, and diurnal trend) suggest that both might come from the same kind of vegetative metabolism. Both isoprene and MBO are sensitive to the main oxidants in the atmosphere such as OH radicals, O 3 , and NO 3 radicals. Isoprene has already been well-studied. The values reported in the literature for the room temperature rate constant of the reaction between ozone and isoprene (k 1 ) were quite dissimilar but they tend to converge to the value of 1.20 × 10 -17 cm 3 molecule -1 s -1 . On the contrary, very few data are available concerning the reactivity