Reaction of hydrogen atoms with cyclopropane in the temperature range 358–550 K
The reaction of hydrogen atoms with cyclopropane (CP) has been investigated at a helium pressure of ca. 5 Torr in the temperature range 358–550 K using a conventional flow-discharge system coupled to a quadrupole mass spectrometer. Two sets of pseudo-first-order experiments were performed: (i) where [CP]≫[H], in which case decay of [H] was measured, and (ii) where [CP]≪[H], in which case formation of CH4, the predominant hydrocarbon product, was measured. To evaluate the rate constant k1 H + c-C3H6→ H2+ c-C3H5(1) computer integration of a detailed mechanism for the overall process has been carried out. We obtain self-consistent values of k1 represented by log (k1/cm3 mol–1 s–1)= 14.21 ± 0.13 –(49.0 ± 1.1 kJ mol–1)/(2.3 RT) which are in accord with the ‘high’ value, 445 kJ mol–1, for the C—H bond dissociation energy in cyclopropane. There is no evidence of curvature in the Arrhenius plot over the range 358–550 K.