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

Abstract

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.