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Kinetics Study of the Reaction of OH Radicals with C5–C8 Cycloalkanes at 240–340 K using the Relative Rate/Discharge Flow/Mass Spectrometry Technique

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journal contribution
posted on 24.10.2013, 00:00 by Sumitpal Singh, Maria Fatima de Leon, Zhuangjie Li
Rate constants of reactions of hydroxyl radical with cyclopentane (k1), cyclohexane (k2), cycloheptane (k3), and cyclooctane (k4) have been acquired at 240–340 K and a total pressure of about 1 Torr using the technique of relative rate combined with discharge flow and mass spectrometry (RR/DF/MS). At 298 K, the rate constants are determined using two reference compounds, which are averaged to be k1 = (4.81 ± 0.88) × 10–12, k2 = (6.41 ± 0.85) × 10–12, k3 = (10.30 ± 1.44) × 10–12, and k4 = (1.42 ± 0.27) × 10–11 cm3 molecule–1 s–1. The Arrhenius expressions at 240–340 K for these reactions are determined to be k1(T) = (2.43 ± 0.50) × 10–11exp­[−(481 ± 58)/T], k2(T) = (3.96 ± 0.60) × 10–11exp­[−554 ± 42)/T], k3(T) = (5.74 ± 0.66) × 10–11exp­[−527 ± 33)/T], and k4(T) = (1.12 ± 0.21) × 10–10exp­[−626 ± 53)/T]. Using the kcycloalkane+OH(277 K) values measured in the present work, the atmospheric lifetime for cyclopentane, cyclohexane, cycloheptane, and cyclooctane is estimated to be about 78, 64, 38, and 29 h, respectively.

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