Rate constants for the gas‐phase reactions of the OH radical with a series of monoterpenes at 294 ± 1 K

Using a relative rate technique, rate constants for the gas‐phase reactions of the OH radical with a series of monoterpenes have been determined in one atmosphere of air at 294 ± 1 K. Relative to a rate constant for the reaction of OH radicals with 2,3‐dimethyl‐2‐butene of 1.12 × 10 −10 cm 3 molecule −1 sec −1 , the rate constants obtained were (in units of 10 −11 cm 3 molecule −1 sec −1 ): α‐Pinene, 5.45 ± 0.32; β‐pinene, 7.95 ± 0.52; Δ 3 ‐carene, 8.70 ± 0.43; d‐limonene, 16.9 ± 0.5; α‐terpinene, 36.0 ± 4.0; γ‐terpinene, 17.6 ± 1.8; α‐phellandrene, 31.0 ± 7.1; myrcene, 21.3 ± 1.6; and ocimene (a cis ‐, trans ‐mixture), 25.0 ± 1.9. These are the first quantitative kinetic data reported for many of these monoterpenes. The rate constants obtained are compared with the available literature data and with a priori estimates based on the number and configuration of substituents around the double bond(s). The tropospheric lifetimes of these monoterpenes with OH radicals, NO 3 radicals and O 3 are estimated and compared. Atmospheric lifetimes with respect to reaction with the OH radical are calculated to range from ∼0.75 hr for α‐terpinene to ∼5 hr for α‐pinene.