INSTRUMENTATION previously proposed from indirect evidence (13,14). By using fast thermolysis/FT-IR, we can readily detect both cis- and trans-HONO in the IR spectrum of the gas from RDX (see the PQR pair at 700-900 cm"1 in Figure 2). However, as shown in Figure 3, HONO is transient under the conditions of the experiment. The initial concentrations most closely reflect the connection of the gas products to the composition of the parent molecule. Figure 4 shows the quantity of HONO as a percentage of the initial gas products for various nitramines (11) versus the H/NO2 ratio in the parent molecule. The general trend suggests that HONO arises from adventitious bimolecular encounters of H' and NO2'
radicals in the condensed phase (11) rather than from concerted decomposition of the 4- and 5-center intermediates (below) that may contribute in unimolecular gas-phase reactions (15).
Fast thermolysis/FT-IR thus far also has made key contributions to uncovering relationships between the parent molecular structure and decomposition
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Figure 4. Plot of the initial relative percent concentration of HONO versus the H/NO2 ratio in the parent molecule for a series of nitramine compounds. DMHDNA = N, N'-dimethyl-W, N'-dinitro-1,6-hexanediamine; MBNA = W-methyl-W-nitro-1-butanamine; frans-TNAD = fraf?s-decahydro-1,3,5,7-tetranitropyrimido[5.4-d]pyrimidine; DNCP = 1,3-dinitroimidazolidine; DNP = W, W'-dinitropiperidine; TNSD = 1,3,7,9-tetranitro-1,3,7,9-tetraazaspiro[4.5]decane; TNSU = 2,4,8,10-tetranitro-2,4,8,10-tetraazaspiro[5.5]undecane; TNDBN = 1,3,5,7-tetranitro-3,7-diazabicyclo[3.3.1]nonane; DMEDNA = N, W'-dimethyl-W, W'-dinitro-1,2-ethanediamine; c/s-TNAD = c/s-(±)-decahydro-1,3,5,7-tetranitropyrimido[5.4-i/]pyrimidine;HNDZ = 1,3,3,5,7,7-hexanitro-1,5-diazacyclooctane; DNNC = 1,3,5,5-tetranitrohexahydropyrimidine; RDX = hexahydro-1,3,5-trinitro-1,3,5-triazine; TNAZ = 1,3,3-trinitroazetidine; HMX = octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine.
900 A · ANALYTICAL CHEMISTRY, VOL. 61, NO. 15, AUGUST 1, 1989
