Rate constants for the gas‐phase reactions of O₃ with a series of Terpenes and OH radical formation from the O₃ reactions with Sesquiterpenes at 296 ± 2 K

Rate constants for the gas‐phase reactions of O₃ with the sesquiterpenes α‐cedrene, α‐copaene, β‐caryophyllene, α‐humulene, and longifolene, and with the monoterpenes limonene, terpinolene, α‐phellandrene, and α‐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 cm³ molecule⁻¹ s⁻¹) are: limonene, 20.1 ± 5.1; terpinolene, 188 ± 67; α‐phellandrene, 298 ± 105; α‐terpinene, 2110 ± 770; α‐cedrene, 2.78 ± 0.71; α‐copaene, 15.8 ± 5.6; β‐caryophyllene, 1160 ± 430; α‐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 O₃ reactions with the sesquiterpenes, of 0.67 for α‐cedrene, 0.35 for α‐copaene, 0.06 for β‐caryophyllene, and 0.22 for α‐humulene, all with estimated overall uncertainties of a factor of ca. 1.5. The tropospheric lifetimes of the sesquiterpenes due to reaction with O₃ are calculated. © 1994 John Wiley & Sons, Inc.