Yu. I. Rubtsov

Kinetics and mechanism of thermal decomposition of hydroxylammonium nitrate

The kinetics of thermal decomposition of melted hydroxylammonium nitrate have been investigated by the rate of heat production in the temperature range 84.8–120.9°C. The decomposition proceeds with autocatalysis and up to 60 % of conversion the rate of the process increases proportionally to the square of the degree of decomposition. The initial rate is proportional to the square of the concentration of HNO3 formed due to dissociation of the salt. The activation energy of this process is 15.3±1.8 kcal/mol. It is suggested that the initial stage the process proceeds via interaction between N2O3 and NH3OH+, whereas the subsequent acceleration is due to oxidation of NH3OH+ by nitrogen oxides formed as well as by nitrous acid.

Kinetics of the thermal decomposition of dinitramide

The kinetic regularities of the thermal decomposition of dinitramide in aqueous solutions of HNO3, in anhydrous acetic acid, and in several other organic solvents were studied. The rate of the decomposition of dinitramide in aqueous HNO3 is determined by the decomposition of mixed anhydride of dinitramide and nitric acid (N4O6) formed in the solution in the reversible reaction. The decomposition of the anhydride is a reason for an increase in the decomposition rates of dinitramide in solutions of HNO3 as compared to those in solutions in H2SO4 and the self-acceleration of the process in concentrated aqueous solutions of dinitramide. The increase in the decomposition rate of nondissociated dinitramide compared to the decomposition rate of the N(NO2)2− anion is explained by a decrease in the order of the N−NO2 bond. The increase in the rate constant of the decomposition of the protonated form of dinitramide compared to the corresponding value for neutral molecules is due to the dehydration mechanism of the reaction.

The standard enthalpies of formation of alkoxy-NNO-azoxy compounds

The standard enthalpies of combustion ΔcHo and formation ΔfHo of seven alkoxy-NNO-azoxy compounds containing the-N+(O−)=NO-characteristic group were determined by combustion in a calorimetric bomb in the atmosphere of oxygen. The contribution of this group to the ΔfHo enthalpies of the substances studied was calculated. The ΔfHo enthalpies found by the method of group contributions were in satisfactory agreement with experimental data.

Kinetics of Oxidation of Organic Acids by Ammonium Nitrate

Kinetics of oxidation of some organic acids by ammonium nitrate was studied. Temperature dependences of the rate constants of acid oxidation were determined.

Equilibrium constants of cellulose nitration by nitric acid under quasi-homogeneous conditions

The equilibrium of nitration of cellulose was studied at 13.1 and 20 °C in aqueous solutions of HNO3 (77.3–80.5 wt.%) forming quasi-homogeneous solutions with cellulose. At 20 °C under quasi-homogeneous conditions, the rates of cellulose nitration are comparable to those of homogeneous nitration of alcohols. The effective nitration constants differ substantially for heterogeneous and homogeneous reactions. Using IR spectra, the partial conversions in the nitration to the 2, 3 and 6 positions of the glucopyranose cycle and the effective equilibrium constants of formation of different isomeric nitrates were estimated.

Equilibrium constants of nitration of alcohols and thermal stability of their nitrates

The data on equilibrium constants of the nitration of polyhydric alcohols and cellulose were examined and generalized. Changes in values of the equilibrium constants and Gibbss energy of nitration related to the position of the nitrated hydroxyl group in the molecule and the existence of the adjacent hydroxyl and nitrate groups were established. An empirical method for calculating rates of thermal decomposition of different nitrate groups using experimental equilibrium constants of nitration was suggested.

Kinetic regularities of the heat release during the reactions of aliphatic hydrocarbons with aqueous HNO3

The kinetics of the heat release during the reactions of aqueous HNO3 withn-heptane andn-octadecane was studied. The kinetic regularities of the reactions of hydrocarbons C7H16−C18H38 with HNO3 and the heats of the reactions were described. At all stages, except initial, the hydrocarbon reacts with NO2 and nitric acid reproduces NO2 in the reaction with NO. The accumulation of NO2 results in the acceleration of the process. When the pressure of the hydrocarbon vapor is equilibrium, its reaction with NO2 can also proceed in the gas phase. The contribution of this reaction to the total heat release was estimated. The additives of aromatic and unsaturated hydrocarbons to aliphatic hydrocarbons increase strongly the initial rate of the heat release and changes slightly the subsequent stages of the process. Naphthenic hydrocarbons have almost no effect on the kinetic parameters of the process.

Kinetics of heat release during the reaction ofn-decane with nitrogen dioxide in the liquid phase

The rates of heat release in the nitrogen dioxide—n-decane system at a molar ratio of nitrogen oxides ton-decane (β) from 2.4·10−3 to 3.1 and gaseous volumes per mole ofn-decane (V(g)) equal to 0.05–4.5 were studied in the 55.2–92.8 °C temperature range. The initial rate of the process is determined by the interaction of NO2 withn-decane. The equilibrium constants of dissociation of N2O4 inn-decane and Henrys constants of NO2 and N2O4 in ann-decane solution were determined by complex analysis of the thermodynamic equilibrium in the NO2—n-decane system and dependences of the initial rates onV(g) and β. The experimentally observed self-acceleration of the process in the region of high β and lowT values was suggested to be due to the reaction of N2O4 with intermediate oxidation products. The rate constants of the reaction of NO2 withn-decane were compared with analogous values determined in its mixtures with HNO3 solutions.

The kinetics of vapor-phase nitration of cellulose 2.* Nitration with nitric acid under static conditions

The regularities of vapor-phase nitration of cellulose with HNO3 under conditions of natural convection and hindered heat removal in the absence of air were studied using the nonisothermal kinetic method. It was established that the nitration rate at the depth of conversion of 0.08 to 0.7 is described by the kinetic law dη/dt =k1p/(1+βη), wherek1 = 104.49±0.6 exp(−A/RT) s−1 atm−1, β = 10−35.5±15.7exp(B/RT),A = 36.6±3.8 kl mol−1, andB = 203±88 kJ mol−1. The diffusion mechanism of vapor-phase nitration of cellulose, which explains the high value of activation energies, is discussed. The effective diffusion coefficient of HNO3 in cellulose at 25 °3.7 · 10−7 cm2 s−1) and the activation energy of diffusion (38.3±4.2 kJ mol−1) were estimated.

Preparation and properties of secondary amides of 1,1-dinitroalkanecarboxylic acids

The previously unknown secondary amides of 1,1-dinitroalkanecarboxylic acids were prepared by the reaction of polynitroimidoyl fluorides with water in the presence of mineral acids. They are inert with respect to electrophiles, but react with nucleophiles with the cleavage of the C-C bond between the carbonyl C atom and the C atom of the dinitromethylene group. An X-ray structural study of the amides was carried out and their thermochemical characteristics were determined.