Kinetics of reactions of C2H radical with acetylene, O-2, methylacetylene,and allene in a pulsed Laval nozzle apparatus at T=103 K

The rate constants of the reactions of C2H radical with HC=CH (k(1)), O-2 ( k(2)), CH3C=CH (k(3)), and H2C=C=CH2 (k(4)) are measured at 103 K using a p ulsed Laval nozzle supersonic expansion and the CH(A(2)Delta) chemiluminesc ence monitor method: k(1) = (1.3 +/- 0.3) x 10(-10), k(2) = (3.8 +/- 0.9) x 10(-11), k(3) = (2.7 +/- 0.6) x 10(-11), and k(4) = (2.5 +/- 0.6) x 10(-10 ) cm(3) molecule(-1) s(-1). These values are compared to previous results a nd measurements in a continuous Laval nozzle apparatus (accompanying paper by Carty et al.). The non-Arrhenius behavior and possible implications of t he results for atmospheric chemistry of Titan are discussed. (C) 2001 Elsev ier Science B.V. All rights reserved.