Detection of autocatalytic decomposition behavior of energetic materials using APTAC

Characterization of autocatalytic decomposition reactions is important for the safe handling and storage of energetic materials. Isothermal differential scanning calorimetry (DSC) has been widely used to detect autocatalytic decomposition of energetic materials. However, isothermal DSC tests are time consuming and the choice of experimental temperature is crucial. This paper shows that an automatic pressure tracking calorimeter (APTAC) can be a reliable and efficient screening tool for the identification of autocatalytic decomposition behavior of energetic materials. Hydroxylamine nitrate (HAN) is an important member of the hydroxylamine family. High concentrations of HAN are used as liquid propellants, and low concentrations of HAN are used primarily in the nuclear industry for decontamination of equipment. Because of its instability and autocatalytic decomposition behavior, HAN has been involved in several incidents.     

The anomeric effect: Ab-initio studies on molecules of the type X?CH2?O?CH3

The anomeric effect of the functional groups X = C?N, C?CH, COOH, COO^?, O? CH₃, NH₂, and NH⁺₃ has been studied with ab initio techniques. Geometry effects upon rotation around the central C? O bond in X? CH₂? O? CH₃ have been compared in the various compounds. The energy differences between the conformers with a gauche and trans (X? C? O? C) arrangement were calculated at the 6-31G* level in the fully optimized 4-21G geometries. Energy differences calculated at the 4-21G level appeared not to be reliable, especially for the groups X that contain non-sp³ hybridized atoms. The 6-31G* energy differences indicate a normal anomeric effect for X = COO^?, O? CH₃, and NH₂(g⁺) (ca. 13 kJ/mol) and a small anomeric effect for X = COOH, C?N, and C?CH (ca. 6 kJ/mol). For X = NH₂(t) and NH⁺₃ a reverse anomeric effect occurs. These observations are in line with experimental results and evidence is given for a competition among various stereoelectronic interactions that occur at the same anomeric center. Geometry variations can be understood in terms of simple rules associated with anomeric orbital interactions. Trends followed when the group X is varied cannot be related in a straightforward way to the energy differences between the trans and the gauche forms in these compounds. Only the variation in the gauche torsion angle X? C? O? C follows roughly the same trend.     

The temperature dependences of saturated vapor pressures and heat capacities of some perfluoropolyethers

The borling temperatures of perfluoro-2,4,6,9,11,13-hexaoxy-n-tetradecane, perfluoro-2,4,6,8,11,13,15,17-octaoxy-n-octadecane, and perfluoro-2,4,6,8,11,13,15,17,19,21-decaoxy-n-docosane were determined by comparative ebulliometry over the saturated vapor pressure range 6.2–101.6 kPa. The heat capacity of perfluoro-2,4,6,8,11,13,15,17-octaoxy-n-octadecane was studied by adiabatic calorimetry over the temperature range 5.3–371.2 K. The densities of the substances at 296–338 K were measured in quartz pycnometers. The data obtained were used to calculate the normal boiling points, enthalpies of vaporization, critical parameters, and thermodynamic functions (entropy, enthalpy, and Gibbs energy) of the polyethers studied.