Suryanarayana Bulusu

Initiation mechanism of TNT: Deuterium isotope effect as an experimental probe

Abstract A large deuterium kinetic isotope effect in the thermal decomposition of methyl deuterated 2,4,6-trini-trotoluene (TNT-α-d3) has been confirmed and tested for its possible influence on the shock sensitivity and detonation velocity. A comparison of the exploding foil shock sensitivity tests and miniature detonation velocity measurements performed on TNT-α-d3 and two differently prepared control samples of unlabeled TNT showed that the former was significantly lower in sensitivity as well as detonation velocity. These results indicate that the rate-determining steps in the controlled condensed phase decomposition and in the chemical mechanism of initiation and detonation are likely to be the same.

MS/MS of energetic compounds. A collisional induced dissociation study of some polynttrobishcmocubanes

Abstract A collisional induced dissociation (CID) study was done on 3,5,5-trinitropentacyclodecane and 5,5-dinitropentacyclodecane-3-carboxylic acid using tandem high-resolution MS/MS. Fragmentation pathways were determined in the El ionization mode. It was found that fragmentation of the C-N bonds–resulting in losses of the NO2groups–takes place before the fragmentation of the C-C bonds.

Investigation of phase transitions in ammonium nitrate by nitrogen–15 nuclear magnetic resonance

Abstract Exploratory Nitrogen-15 nuclear magnetic resonance (NMR) studies of ammonium nitrate (AN) have been undertaken using both conventional and magic angle spinning (MAS) methods. The chemical shift anisotropy is measured by two different methods at room temperature, and a precise measurement of the difference in isotropic chemical shift occurring at the phase transition IV to III is reported. Finally, the activation energy for the motion of both ions in the room temperature phase are obtained. No evidence in discontinuity of nitrogen relaxation times across the phase boundary at 32°C was observed.

Solid-phase thermal decomposition of 2,4-dinitroimidazole (2,4-DNI)

The solid-phase thermal decomposition of the insensitive energetic nitroaromatic heterocycle 2,4-dinitroimidazole (2,4-DNI: mp 265--274C) is studied utilizing simultaneous thermogravimetric modulated beam mass spectrometry (STMBMS) between 200 and 247C. The pyrolysis products have been identified using perdeuterated and {sup 15}N-labeled isotopomers. The products consist of low molecular-weight gases and a thermally stable solid residue. The major gaseous products are NO, CO{sub 2}, CO, N{sub 2}, HNCO and H{sub 2}O. Minor gaseous products are HCN, C{sub 2}N{sub 2}, NO{sub 2}, C{sub 3}H{sub 4}N{sub 2}, C{sub 3}H{sub 3}N{sub 3}O and NH{sub 3}. The elemental formula of the residue is C{sub 2}HN{sub 2}O and FTIR analysis suggests that it is polyurea- and polycarbamate-like in nature. Rates of formation of the gaseous products and their respective quantities have been determined for a typical isothermal decomposition experiment at 235C. The temporal behaviors of the gas formation rates indicate that the overall decomposition is characterized by a sequence of four events; (1) an early decomposition period induced by impurities and water, (2) an induction period where C0{sub 2} and NO are the primary products formed at relatively constant rates, (3) an autoacceleratory period that peaks when the sample is depleted and (4) a final period in which the residue decomposes. Arrhenius parameters for the induction period are E{sub a} = 46.9 {plus_minus} 0.7 kcal/mol and Log(A) = 16.3 {plus_minus} 0.3. Decomposition pathways that are consistent with the data are presented.

Nitrogen-15 nuclear magnetic resonance spectroscopy. Spin-coupling between directly bonded 15N-nuclei

15 N–15N Coupling constants were obtained for several doubly labelled compounds including cyclic and acyclic nitroamines, whcih show a correlation with the hydridization of the nitrogen atoms and the conformation of the nitroamine group.