RATE CONSTANTS FOR THE GAS-PHASE REACTIONS OF O-3 WITH A SERIES OF TERPENES AND OH RADICAL FORMATION FROM THE O-3 REACTIONS WITH SESQUITERPENES AT 296+/-2-K

Rate constants for the gas-phase reactions of O-3 With the sesquiterpenes alpha-cedrene, alpha-copaene, beta-caryophyllene, alpha-humulene, and longifolene, and with the monoterpenes limonene, terpinolene, alpha-phellandrene, and alpha-terpinene, have been measured using a relative rate technique at 296 +/- 2 K and atmospheric pressure of air. The rate constants obtained (in units of 10(-17) cm(3) molecule(-1) s(-1)) are: limonene, 20.1 +/- 5.1; terpinolene, 188 +/- 67; alpha-phellandrene, 298 +/- 105; alpha-terpinene, 2110 +/- 770; alpha-cedrene, 2.78 +/- 0.71; alpha-copaene, 15.8 +/- 5.6; beta-caryophyllene, 1160 +/- 430; alpha-humulene, 1170 +/- 450; and longifolene, <0.07, where the indicated errors include the estimated overall uncertainties in the rate constants for the reference organics. Hydroxyl radical formation yields were also determined for the O-3 reactions with the sesquiterpenes, of 0.67 for alpha-cedrene, 0.35 for alpha-copaene, 0.06 for beta-caryophyllene, and 0.22 for alpha-humulene, all with estimated overall uncertainties of a factor of ca. 1.5. The tropospheric lifetimes of the sesquiterpenes due to reaction with O-3 are calculated. (C) 1994 John Wiley & Sons, Inc.