OH RADICAL FORMATION YIELDS FROM THE GAS-PHASE REACTIONS OF O-3 WITH ALKENES AND MONOTERPENES

The compound 2-butanol has been used to scavenge greater than or equal to 95% of the OH radicals formed in the reactions of O-3 with the alk enes 2,3-dimethyl-2-butene and 2-methyl-2-butene and with the monoterp enes alpha-pinene and sabinene at 296 +/- 2 K and atmospheric pressure of air, with the OH radical formation yields from these O-3 reactions being obtained from the amounts of 2-butanone formed. The rate consta nt for the reaction of the OH radical with 2-butanol was measured usin g a relative rate method; the rate constant was determined to be (9.2 +/- 2.4) x 10(-12) cm(3) molecule(-1) s(-1) at 296 +/- 2 K, where the indicated error includes the estimated overall uncertainties in the ra te constant for the reference organic (cyclohexane). The formation yie ld of 2-butanone from the reaction of the OH radical with 2-butanol wa s determined to be 0.695 +/- 0.073. Using this 2-butanone formation yi eld from the OH radical reaction with 2-butanol, the OH radical format ion yields from the reactions of O-3 with 2,3-dimethyl-2-butene, 2-met hyl-2-butene, alpha-pinene, and sabinene were determined to be 0.80 +/ - 0.12, 0.93 +/- 0.14, 0.76 +/- 0.11, and 0.33 +/- 0.06, respectively. These OH radical formation yields agree to within +/-25% with the yie lds previously derived using cyclohexane to scavenge OH radicals and m easuring the amounts of cyclohexanone plus cyclohexanol formed. Our pr esent OH radical formation yield for 2,3-dimethyl-2-butene is also in good agreement with the value of 0.7 previously reported from a compre hensive product study.