E.s.r. studies of the reactions of atomic oxygen and hydrogen with simple hydrocarbons

Abstract

Electron spin resonance has been used to study the reaction of oxygen atoms in a nitrogen carrier and of hydrogen atoms in an argon carrier with simple hydrocarbons in a fast flow system at total pressures around 2 mm Hg. The reaction between oxygen atoms and acetylene occurs predominantly by the mechanism: O+C2H2= CH2+CO (3) O+CH2= CO+2H (6) CH2+C2H2= C3H4(12) where k3=(9.2 ± 0.4)× 1010 cm3 mole–1 sec–1 and k6=(2.7 ± 1.0)k12 both at 298°K. The initial step in the reaction of oxygen atoms with methyl acetylene is O+CH3 . C CH = CH3 . CH : + CO (13) with k13=(4 ± 1)× 1011 cm3 mole–1 sec–1 at 298°K; the total rate constant for the disappearance of oxygen atoms being 3–4 times greater.