Reaction between hydroxyl (deuteroxyl) radicals and carbon monoxide at temperatures down to 80 K: experiment and theory

Using the pulsed laser-photolysis (PLP) laser-induced fluorescence (LIF) method, rate constants have been measured at low total pressure for the reactions between OH and CO (297≥T/K≥80) and OD+CO (295≥T/K≥178). Calculations have been carried out based on transition-state and RRKM theories and allowing approximately for quantum mechanical tunneling through the transition state (TS2) which separates HOCO (DOCO) from H(D)+CO 2 . They indicate (a) that tunneling is important in both these systems, (b) that the barrier at TS2 is higher than previously thought and closer to the ab initio value, and (c) that the observed kinetic isotope effect can be reproduced quite well. The possible role of hydrogen-bonded complexes in facilitating these reactions is discussed briefly