Formation of organic nitro-compounds in flowing H2O2+ NO2+ N2+organic vapour systems. Part 1.—Surface initiation efficiency and reactions of ethane

When H2O2 vapour is added to an excess of NO2 in a flow system with ethane as the carrier gas in the presence of a boric-acid-coated surface at temperatures in the range 298–363 K, the organic products are nitroethane, ethyl nitrate and smaller amounts of ethyl nitrite. On the basis of the initiating steps [graphic omitted] the total yield of nitro-compounds, extrapolated to [NO2]= 0, provides a direct measure of the H2O2 to OH conversion efficiency in step (1). This is shown to correspond to that indicated by the previously applied indirect method involving measurement of the variation of CO2 yields with the ratio [S]/[CO] in H2O2+NO2+CO systems containing diethyl ether (S) as the internal kinetic calibrant. This efficiency does not change significantly throughout the above temperature range.The mechanism of formation of the nitrocompounds involves the following competitive steps: [graphic omitted] Arguments are presented that step (8) may proceed by way of partial dissociation of chemically activated C2H5ONO molecules rather than by a bimolecular O-abstraction route.A rate constant of k4=(1.3±0.2)× 1010 dm3 mol–1 s–1 is obtained for the reaction OH + NO2(+ M)→ HNO3(+ M)(4) at ambient temperature for M = C2H6 at a pressure of 40 kPa.