Yields of singlet nitrenes from halogen atom—azide molecule reactions

Chemiluminescence from the a 1 Δ and b 1 Σ + excited electronic states of nitrogen halide diatomics is observed when HN 3 is allowed to react with mixtures of halogen atoms in a discharge‐flow apparatus. Excited NF ( a 1 Δ) is produced by the F + HN 3 reaction, and NCl (a 1 Δ, b 1 Σ + ) and NBr ( a 1 Δ, b 1 Σ + ) are produced by the F, Cl, + HN 3 and F, Br + HN 3 reactions, respectively. In the low‐density limit, the yield of NF( a 1 Δ) was found to be near unity. The yields of the b 1 Σ + states of NCl and NBr were determined to have a lower limit of ca. 10%. A number of results from these experiments, including direct observation of N 3 radicals in the flow, support a hypothetical mechanism in which N 3 acts as an intermediate. A second possible mechanism proceeding via an HNF intermediate cannot be ruled out.