Rj. Hoobler et Sr. Leone, Low-temperature rate coefficients for reactions of the ethynyl radical (C2H) with C3H4 isomers methylacetylene and allene, J PHYS CH A, 103(10), 1999, pp. 1342-1346
Low-temperature rate coefficients for the reactions C2H + C3H4 --> products
[C3H4 = methylacetylene (propyne) CH3CCH and allene (propadiene) CH2CCH2]
are measured over the temperature range of 155-298 K. Absolute rate constan
ts are determined using laser photolysis and transient infrared absorption
spectroscopy. Both reactions are fast, approaching the kinetic limit and ha
ve either no temperature dependence or a slight negative temperature depend
ence. Over the experimental temperature range, the rate constants are fit t
o the following Arrhenius expressions: k(CH3CCH) = (1.6 +/- 0.4) X 10(-10)
exp[(71 +/- 50)/T] cm(3) molecule(-1) s(-1) and k(CH2CCH2) = (1.3 +/- 0.6)
x 10(-10) exp[(103 +/- 136)/T] cm(3) molecule(-1) s(-1). The corresponding
rate constants at 298 K are k(CH3CCH) = (1.9 +/- 0.3) X 10(-10) cm(3) molec
ule(-1) s(-1) and k(CH2CCH2) = (1.7 +/- 0.3) X 10(-10) cm(3) molecule(-1) s
(-1). These measurements provide new reaction rate coefficients for the eth
ynyl radical, C2H, with C3H4 unsaturated hydrocarbons. These are necessary
to extend current photochemical models of Jupiter, Saturn, and its satellit
e Titan.