Kinetics and mechanism of the thermal decomposition of dimethylnitramine at low temperatures

Abstract

Dimethylnitramine (DMNA) was pyrolyzed between 466 and 524 K at about 475 Torr pure DMNA pressure in static cells. A radical mechanism was proposed and computer-modeled to account for the disappearance of DMNA and the production of (CH₃)₂NNO and CH₃NO₂. The rate constant for DMNA decomposition into (CH₃)₂N and NO₂, based on these low-temperature results and other high-temperature shock tube data, covering 460–960 K, can be given by k₁ = 10^15.9±0.2 exp(?22,000±200/T) sec^?1. This result leads to values for the N-N bond energy of 43.3±0.5 kcal/mole and the heat of formation of the (CH₃)₂N radical, 35±2 kcal/mole at 298 K. Kinetic modeling of the CH₃NO₂ and (CH₃)₂NNO production profiles has been carried out.     

Kinetics of Escherichia coli inactivation employing hydrogen peroxide at varying temperatures,pH and concentrations

The effectiveness of hydrogen peroxide on the destruction of planktonic cells of Escherichia coli at different temperatures, pH and sanitizer concentrations was studied. Inactivation kinetics of E. coli exhibited a clear dependence on hydrogen peroxide concentration, pH and temperature. A Weibullian mathematical model successfully described the inactivation curves. Quantitative kinetic results obtained allowed to identify various combinations H₂O₂ concentration–pH–temperature for 5-log cycles reduction of E. coli. Flow cytometry analysis revealed induced H₂O₂ cytoplasm membrane damage. TEM observations indicated that H₂O₂ treatment resulted in rupture of outer and cytoplasm membranes and a more uniform granularity.     

DFT calculations of the thermochemistry and structures of tetrazine derivatives

Abstract

Enthalpies of formation and standard state entropies were calculated for tetrazine, amino- and nitrotetrazines, and four extended ditetrazines using DFT programs. The derived values were corrected with the previously derived supplementary set of four parameters. The basic geometric structural features of the minimum energy states of the tetrazines are summarized.     

Study of the liquid-vapor critical temperatures for methyladamantanes and their mixtures with cyclohexane

The liquid-vapor critical temperatures of individual 1,3-dimethyl-and 1,3,5-trimethyladamantanes and their binary mixtures with cyclohexane were determined over the entire range of composition by means of the ampule method. It was found that an excess of the critical temperatures over calculated values reached 20 K for both mixtures studied. The predictive capabilities of several calculation methods are discussed.     

Wettability/spreading of alkanes at the water–gas interface at elevated temperatures and pressures

The Hamaker–Lifshitz theory is used to calculate the spreading coefficient of alkanes on water or brine at elevated temperatures and pressures. The dielectric polarizability at elevated temperature and pressure is estimated as a function of density through the Clausius–Mosotti equation. When complete data is not available, the wetting transition can be estimated from the refractive index at elevated temperatures and pressures. The spreading of alkanes on brine can also be estimated from the refractive index of the brine as a function of electrolyte concentration. The approach used here for alkanes is also used to estimate the conditions for the spreading of H₂S between water and sulfur.