?Rate Coefficient and Mechanism of the OH-initiated Degradation of Cyclobutanol: A Combined Experimental and Theoretical Study?

M. A. GARAVAGNO; F. J. HERNÁNDEZ; R. A. JARA-TORO; G. MAHECHA; J. BARRERA; R. A. TACCONE; G. A. PINO *

ATMOSPHERIC ENVIRONMENT

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2021 vol. 268 p. 118821 - 118831

1352-2310

The degradation process of cyclobutanol (cButOH) by hydroxyl radical (OH), under atmospheric conditions,(750 ± 10) Torr of air and (296 ± 2) K, has been studied. The rate coefficient for the title reaction (k296K = (7.3± 0.6) x 10􀀀 12 cm3 molecule􀀀 1 s􀀀 1) was determined at 296 K by the conventional relative-rate method. Electronicstructure calculations with uCCSD(T)/uBHandHLYP/aug-cc-PVDZ were conducted to study the reactionmechanism. The global rate coefficient was also calculated using the transition state theory with tunnellingcorrections, obtaining a value of 5.4 × 10􀀀 12 cm3 molecule􀀀 1 s􀀀 1 in agreement with the experimental determination.Additionally, reaction products identification in clean and NOx-contaminated atmospheres was performedfor the first time. The identified reaction products and their corresponding yields (YP) depend on theenvironment composition in which the reaction is studied. In the absence of NOx, cyclobutanone (cButanone)was the only identified product, with YcButanone = (0.66 ± 0.08). In NOx-contaminated atmospheres, in addition tocButanone, tetrahydrofuran (THF), 2-nitro-1-butanol (2N1B), 3-nitro-2-butanol (3N2B) and 2-methyl-2-nitro-1-propanol (2M2N1P), were also identified as primary reaction products. Under this condition, we were able to determine only the yields of cButanone and THF (YcButanone = 0.38 ± 0.05 and YTHF = 0.28 ± 0.02). A likelyreaction mechanism for the observed products is proposed and the atmospheric implications are discussed.