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

Rate constants of reactions of hydroxyl radical with cyclopentane (k(1)), cyclohexane (k(2)), cycloheptane (k(3)), and cydooctane (k(4)) 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 k(1), = (4.81 +/- 0.88) x 10(-12), k(2) = (6.41 +/- 0.85) X 10-12, k(3) = (10.30 +/- 1.44) x 10(-12), and k(4) = (1.42 +/- 0.27) X 10(-11) cm(3) molecule(-1) s(-1). The Arrhenius expressions at 240-340 K for these reactions are determined to be k(1)(T) = (2.43 +/- 0.50) x 10(-11)exp[-(481 +/- 58)/T], k2(T) = (3.96 +/- 0.60) X 10(-11)exp[-554 +/- 42)/T], k(3)(T) = (5.74 +/- 0.66) x 10(-11)exp[-527 +/- 33)/T], and k(4)(T) = (1.12 +/- 0.21) x 10(-10)wexp[-626 +/- 53)/T]. Using the k (cyclalkane+OH) (277 K) values measured in the present work, the atmospheric lifetime for cyclopentane, cydohexane, cycloheptane, and cyclooctane is estimated to be about 78, 64, 38, and 29 h, respectively.