Gas‐phase ozonolysis: Rate coefficients for a series of terpenes and rate coefficients and OH yields for 2‐methyl‐2‐butene and 2,3‐dimethyl‐2‐butene

The kinetics of the gas‐phase reactions of O 3 with a series of selected terpenes has been investigated under flow‐tube conditions at a pressure of 100 mbar synthetic air at 295 ± 0.5 K. In the presence of a large excess of m ‐xylene as an OH radical scavenger, rate coefficients k (O 3 +terpene) were obtained with a relative rate technique, (unit: cm 3 molecule −1 s −1 , errors represent 2σ): α‐pinene: (1.1 ± 0.2) × 10 −16 , 3 Δ‐carene: (5.9 ± 1.0) × 10 −17 , limonene: (2.5 ± 0.3) × 10 −16 , myrcene: (4.8 ± 0.6) × 10 −16 , trans ‐ocimene: (5.5 ± 0.8) × 10 −16 , terpinolene: (1.6 ± 0.4) × 10 −15 and α‐terpinene: (1.5 ± 0.4) × 10 −14 . Absolute rate coefficients for the reaction of O 3 with the used reference substances (2‐methyl‐2‐butene and 2,3‐dimethyl‐2‐butene) were measured in a stopped‐flow system at a pressure of 500 mbar synthetic air at 295 ± 2 K using FT‐IR spectroscopy, (unit: cm 3 molecule −1 s −1 , errors represent 2σ ): 2‐methyl‐2‐butene: (4.1 ± 0.5) × 10 −16 and 2,3‐dimethyl‐2‐butene: (1.0 ± 0.2) × 10 −15 . In addition, OH radical yields were found to be 0.47 ± 0.04 for 2‐methyl‐2‐butene and 0.77 ± 0.04 for 2,3‐dimethyl‐2‐butene. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 394–403, 2002