Hydroxyl-Radical Kinetics by Kinetic Spectroscopy. II. Reactions with C2H6, C3H8, and <i>iso</i>-C4H10 at 300°K

Abstract

Gas-phase, room-temperature reactions of the OH radical with C2H6, C3H8, and iso-C4H10 were studied with the flash-photolysis—kinetic-spectroscopy (KS) technique. Rate constants (in units of cubic centimeters per mole·second) were obtained as follows: C2H6+OH→C2H5+H2O, k3=1.76±0.23×1011 at 302∘±2∘K,C3H8+OH→C3H7+H2O, k4=8.2±1.2×1011 at 298∘±1∘K,iso−C4H10+OH→C4H9+H2O, k5=1.28±0.07×1012 at 297∘±1∘K.It is shown that relative theoretical values for frequency factor ratios and Evans—Polanyi activation energies are inconsistent with the ratios of the observed rate constants for H abstraction by OH from these alkanes.