KINETICS OF THE GAS-PHASE REACTIONS OF OH AND NO3 RADICALS WITH 2-CARENE, 1,8-CINEOLE, PARA-CYMENE, AND TERPINOLENE

Rate constants for the gas-phase reactions of OH and NO3 radicals with the biogenically emitted monoterpenes 2-carene and terpinolene and the related compounds 1, 8-cineole and p-cymene have been determined at 295 ± 2 K and atmospheric pressure by using relative rate methods. The rate constants obtained were (cm3 molecule−1 s−1) as follows. For reaction with the OH radical: 2-carene, 7.95 × 10−11; 1, 8-cineole, 1.11 × 10−11 p-cymene, 1.51 × 10−11; terpinolene, 2.25 × 10−10. For reaction with the NO3 radical: 2-carene, 1.94 × 10−11; 1, 8-cineole, 1.7 × 10−16; p-cymene, 9.9 × 10−16; terpinolene, 9.62 × 10−11. Combined with the rate data for the corresponding reactions of these compounds with O3 and the ambient tropospheric concentrations of OH and NO3 radicals and O3, these data show that the OH and NO3 radical and O3 reactions must all be considered as loss processes for 2-carene and terpinolene, with calculated lifetimes of 2-carene and terpinolene of 2 h or less. For 1, 8-cineole and p-cymene, only the OH radical reactions will of importance, with tropospheric lifetimes of 1, 8-cineole and p-cymene of 1.0–1.4 days being calculated. © 1990, American Chemical Society. All rights reserved.