Determination of relative rates for oxygen atom-hydrocarbon reactions by reduction of oxygen atom, nitric oxide chemiluminescence

Abstract

Relative rates of reaction between oxygen atoms and hydrocarbons have been determined at 25°C ± 5°C. With reference to isobutene, the relative rates for ethylene, propylene, 1‐butene, cis‐2‐butene, trans‐2‐butene, 1,3 butadiene, and 3‐methylbutene‐1 are: 0.042 ± 0.010, 0.20 ± 0.05, 0.18 ± 0.07, 0.79 ± 0.25, 1.25 ± 0.35, 0.96 ± 0.35, and 0.22 ± 0.05. Hydrocarbons and oxygen atoms are mixed prior to detection of the oxygen atoms by their chemiluminescent reaction with nitric oxide. The chemiluminescent signal is simply related to the product of the gas‐phase contact time, the hydrocarbon concentration, and the reaction rate constant for the oxygen atom‐hydrocarbon reaction. With an oxygen atom concentration of approximately 10⁷ cm⁻³ at a system pressure of 10 torr, olefinic hydrocarbon concentrations as low as 1.0 parts‐per‐million are used to establish the relative rates.