Showing papers on "Chemical decomposition published in 1977"

Deuterium isotope effects in the thermochemical decomposition of liquid 2,4,6-trinitrotoluene: application to mechanistic studies using isothermal differential scanning calorimetry analysis

Abstract: The thermochemical decomposition of liquid 2,4,6-trinitrotoluene (TNT) produces a primary kinetic deuterium isotope effect when its methyl moiety is deuterium labeled. The novel integration of the deuterium isotope effect with isothermal differential scanning calorimetry analysis provides the first directly measured mechanistic evidence that carbon-hydrogen bond rupture in the TNT methyl group constitutes the rate-determining step of the thermochemical decomposition reaction. This thermochemical reaction possesses an induction period during which a single species forms from TNT and catalyzes a sustained exothermic decomposition. An expression was derived that correlated deuterium/hydrogen induction time ratios with inaccessible hydrogen/deuterium rate constant ratios during this induction period. Direct induction time measurement allowed deuterium isotope effect evaluation before interfering side reactions diluted the magnitude of the isotope effect during the latter stages of exothermic decomposition. Hydrogen donor effects suggest that the rate-determining carbon-hydrogen bond rupture proceeds homolytically. A large negative entropy of activation reveals a high degree of orderliness during the decomposition.

Effusion studies of the thermal decomposition of magnesium and calcium sulfates

Abstract: The torsion‐effusion method, with simultaneous torque angle and weight loss measurements, was used to study the thermal decomposition of MgSO4 and CaSO4. The initial step in the decomposition/vaporization process appears to be the evolution of an SO3 molecule from the lattice, followed by conversion to SO2 and O2 on the surface. Measurements of decomposition pressure as a function of orifice area show that both steps are kinetically hindered. The experimental results can be correlated very satisfactorily by the Whitman–Motzfeldt model, so that reliable equilibrium data can be derived despite large degrees of undersaturation of the vapors. With MgSO4 it was possible to evaluate both the SO3 and SO2+O2 equilibrium pressures, the latter by addition of a small amount of Fe2O3 catalyst to the sample. Analysis of the derived equilibrium pressures yields values of −310.3±0.5 and −344.8±0.5 kcal/mol for the standard enthalpies of formation of MgSO4(s) and CaSO4(s), respectively, at 298 K.

The influence of the environment on the thermal decomposition of oxysalts

Abstract: The environment can influence the thermal decomposition of an oxysalt by; (a) causing a change in the course of chemical decomposition or (b) causing an alteration in the physical nature of the solid product or solid intermediates.

A study of the chemical degradation of ClONO2 in the stratosphere

Abstract: The flash photolysis-resonance fluorescence system described by Davis et al (1974) is used to measure the rate constants for the reactions of chlorine nitrate (ClONO2) with stratospheric O(3-P) and OH Both reactions are examined in a pyrex cell with an internal volume of about 150 cu cm, where the reaction mixture was maintained at 245 K by circulating methanol from a thermostated circulation bath through the outer jacket of the reaction cell The relative chemical degradation rates as a function of altitude for both reactions are tabulated, which shows that the chemical degradation pathways contribute less than 10% to the total rate of ClONO2 destruction at altitudes less than 30 km Since the concentration of ClONO2 is calculated to be near its maximum around 25 km and drops off very significantly at higher altitudes, it is concluded that the photochemical decomposition of ClONO2 in the stratosphere is by far the most important degradation path for this molecule

Kinetics of the thermal decomposition of hydrogen sulfide behind shock waves

Abstract: The thermal decomposition of H 2 S behind incident shock waves in H 2 S−Ar mixtures was studied over the temperature range 2700–3800°K for total concentrations in the range 2×10 −6 to 7×10 −6 mole/cc. During reaction, the H 2 S concentration was monitored using an ultraviolet absorption spectroscopic technique, and the S-atom concentration was inferred from measurements of the absolute intensity of emission from electronically-excited S 2 . Detailed information on the decomposition mechanism was obtained by comparing measured H 2 S and S-atom concentration profiles with results from a computer simulation of the reaction. During the decomposition reaction, measured concentration profiles could be modelled adequately using a six-reaction mechanism. For the conditions investigated, the primary decomposition step was shown to be second-order. H 2 S+ M →SH+H+ M with a rate coefficient, for argon as a collision partner, given by K 1 Ar =10 14.3 exp(−310 kJ/RT) cc/mole·sec.

Effect of Oxygen on the Polymerization of Vinyl Chloride

Abstract: The effects of oxygen on the liquid-phase polymerization of vinyl chloride at 55°C in the presence of an added initiator, bis(4-tert-butylcyclohexy1) peroxydicarbonate, (Perkadox 16), have been studied by tumbled dilatometry. A conventional kinetic scheme involving a predominant cross-termination reaction is proposed to explaine the dependence of the induction period on initial oxygen concentration and initiator concentration. The degree of conversion of the initial oxygen to peroxidic compounds did not exceed 30% by weight under any experimental conditions employed, and the existence of other oxidation products such as formaldehyde, carbon monoxide, and methanol has been demonstrated. Radical decomposition reactions may produce some of the oxidation products. At 55°C, the average velocity constant for decomposition of vinyl chloride polyperoxides in dichloromethane solution was 8 × 10−5 sec−1 compared with 6.6 × 10−5 sec−1 for Perkadox 16. Perkadox 16 has been used as an initiator in a dilatomet...

Consecutive reactions in the thermal decomposition of phenylalkyldiazirines

Abstract: The thermal decomposition of phenyl-n-butyldiazirine and of phenylmethyldiazirine in DMSO and in HOAc have been investigated over the temperature range 80–130 °C. The intermediate diazo compounds, 1-phenyl-1-diazopentane and 1-phenyldiazoethane respectively have been detected and isolated. The decomposition of phenyl-n-butyldiazirine and the subsequent decomposition of its product, 1-phenyl-1-diazopentane, are an illustration of consecutive reactions. The kinetic parameters for the isomerization and decomposition reactions have been determined. The isomerization of phenylmethyldiazirine to 1-phenyldiazoethane is first order and probably unimolecular but the kinetics for the subsequent reactions of 1-phenyldiazoethane are complicated by several competing rate processes.

Computer simulation of loss of fertilizer nitrogen through chemical decomposition of nitrite

Abstract: Summary An estimate is given of nitrogen losses which could occur through chemical decomposition of nitrite formed by nitrification of ammonium in acid tropical soils. Experiments on the rate of disappearance of nitrite were carried out in acid buffers as well as in soil samples. Numerical solutions of a system of differential equations describe the nitrification process and the chemical denitrification reaction. Up to 50 per cent of added ammonium nitrogen may be lost in an acid soil when nitrification occurs at temperatures prevailing in the humid tropics.

Catalytic Decomposition of Nitric Oxide in the Presence of Alkaline Earth Oxides

Abstract: The alkaline earth oxides of barium, strontium, and calcium have been studied as catalysts for the decomposition of nitric oxide. The low work function characterizing these oxides is liable to favor an electron donor catalytic process which decomposes the nitric oxide molecule. The latter was used diluted in helium and the concentration was varied between 0.5 and 2.5%. Experiments were carried out at 650, 750, and 850/sup 0/C. After passage over the catalyst, nitric and nitrous oxides were found in the gaseous phase, as well as nitrogen and oxygen. It was found that the decomposition reaction rates of nitric and nitrous oxides are mutually independent. Reaction rate constants were calculated, showing that constants related to nitric oxide were at least one order of magnitude higher than those related to nitrous oxide thus explaining the independent behavior. The total conversion for nitric oxide was highest for barium oxide, attaining 80% at 850/sup 0/C, followed by strontium and calcium oxides. Increasing efficiencies coincide with a decrease in work function. Within the limits of nitric oxide used, up to 3% oxygen do not show any inhibitive effect on nitric oxide decomposition. (17 fig.)

Decomposition of 1-phenylethyl hydroperoxide in the presence of cobalt acetylacetonates

Abstract: The decomposition of 1-phenylethyl hydroperoxide has been investigated in the presence of Co(acac)2 and Co(acac)3 in argon and oxygen atmospheres. Co(acac)2 accelerates the decomposition of the hydroperoxide. The decomposition is preceded by the fast formation of a Co(acac)2+ ROOH complex which is unaffected by the presence of oxygen in the temperature range studied. The deactivation of the catalyst by the water formed in the decomposition reaction has been confirmed from kinetic evidence. The rate constants for the formation and decomposition of the catalyst + ROOH complex and the overall activation energy were determined.In the presence of Co(acac)3 the decomposition starts after an induction period being longer in oxygen than in argon. It is assumed that the actual catalyst of this process is also Co(acac)2. The overall activation energy of the decomposition has been determined.

Method of preparing catalyst for decomposing hydrocarbon and ammonia

Abstract: PURPOSE:A method of preparing a catalyst which does not become powder and can maintain its high activity over a long time when used in decomposition reaction of hydrocarbon into mainly CO and H2, and which has excellent low temperature activity when used in decomposition reaction of ammonia into N2 and H2.

宗谷 (天北) 炭の高圧水素化分解反応機構

Abstract: High pressure hydrogenolysis reaction was carried out on Sohya coal (Tempoku) and the various structural parameters of the reaction products were obtained. Based on a follow up of the changes accompanying the reaction, an analysis of hydrogenolytic reaction mechanism of Sohya coal and chemical structure characteristics were discussed and the following conclusions were led forth.In the hydrogenolysis of Sohya coal under conditions of reaction temperature at 400°C and reaction pressure of 220kg/cm2, it was considered that an in parallel progress of saturation and decomposition of the aromatic condensed ring, cleavage of structural unit bond, dealkylation reaction was present. It was also recognized that the hydrogenolytic reactivity of Sohya coal was higher as compared with other Hokkaido coals. In addition in the present study in which vehicle oil is not used, at the initial stages of the reaction the progress of the reaction which directly produces oil from coal is seen and it is surmized that a successive decomposition reaction proceeds following the above, from coal→asphaltene→oil.The mean number of aromatic condensed rings of the strucutral unit of the main portion of Sohya coal is 2 or thereabouts, and the hydrocarbon side chain is shorter compared with other Hokkaido coals with an average carbon number of 1.6 or thereabouts.

Thermal decomposition of nitrosyl cyanide

Abstract: The stoichiometry of the thermal decomposition of nitrosyl cyanide was investigated. Nitrogen-15 was used as a tracer to obtain information about the mechanism of the reaction. (LK)

Catalytic properties of sodium-containing silica gel in n-heptane decomposition

Abstract: n-Heptane decomposition reactions on silica catalysts containing various amounts of sodium ions were studied. Ethylene, methane and propylene as well as unbrached α-olefins were the main reaction products. The comparison of the experimental and theoretical results suggests a free-radical reaction mechanism.

Six-membered cyclic diacyl peroxide fragmentations. Thermal decomposition of meso- and dl-2,3-dimethylsuccinoyl peroxides

Abstract: We report the syntheses and thermal decomposition of meso- and dl-2,3-dimethylsuccinoyl peroxides (1 and 2, respectively). These initial findings provide the first stereochemical study of six-membered cyclic diacyl peroxide thermal fragmentations. The data presented here are consistent with a common intermediate(s) but do not require the generation of electronically excited states of the 2-butene products.

Catalytic decomposition of nitric oxide in the presence of alkaline earth oxides

Abstract: The alkaline earth oxides of barium, strontium, and calcium have been studied as catalysts for the decomposition of nitric oxide. The low work function characterizing these oxides is liable to favor an electron donor catalytic process which decomposes the nitric oxide molecule. The latter was used diluted in helium and the concentration was varied between 0.5 and 2.5%. Experiments were carried out at 650, 750, and 850/sup 0/C. After passage over the catalyst, nitric and nitrous oxides were found in the gaseous phase, as well as nitrogen and oxygen. It was found that the decomposition reaction rates of nitric and nitrous oxides are mutually independent. Reaction rate constants were calculated, showing that constants related to nitric oxide were at least one order of magnitude higher than those related to nitrous oxide thus explaining the independent behavior. The total conversion for nitric oxide was highest for barium oxide, attaining 80% at 850/sup 0/C, followed by strontium and calcium oxides. Increasing efficiencies coincide with a decrease in work function. Within the limits of nitric oxide used, up to 3% oxygen do not show any inhibitive effect on nitric oxide decomposition. (17 fig.)

Unstable halogenated organolithium compounds III. Mechanism of the formation of biphenylene in the decomposition of o-halo derivatives of phenyllithium

Abstract: 1. The formation of biphenylene in the decomposition of o-halophenyllithiums takes place with the intermediate participation of the corresponding 2-halo-2′-lithiobiphenyls, the cyclization of which into biphenylene is considerably accelerated by adsorption or by complex-formation with aromatic compounds. 2. On the basis of decomposition reactions of o-halophenyllithiums, a method has been developed for the synthesis of biphenylene with a yield of 50–60%.