Showing papers on "Chemical decomposition published in 1976"

Stabilization of solutions of 3-isothiazolones

Abstract: Solutions of 3-isothiazolones are stabilized against chemical decomposition of the isothiazolone by adding thereto a metal nitrate or a metal nitrite.

Kinetics of endothermic decomposition reactions. I. Steady-state chemical steps

Abstract: When the solid product of an endothermic decomposition reaction is porous, the rate-limiting chemical step is usually assumed to be a surface step of the gaseous product or of a precursor of that product It is shown here that the rate of such a reaction may also depend upon rates of diffusion in the reactant phase, the rate of transfer of the solid reaction product at the reactant-product interface, and/or the thermodynamic stability of the solid product Rate equations are derived for the six possible limiting cases when either a single step or a coupled pair of steps of a decomposition reaction significantly influence its rate Data for calcite (CaCO/sub 3/) decomposition are shown to be most simply explained as reflecting formation of a known metastable modification of calcium oxide with near equilibrium conditions maintained for each reaction step except desorption of carbon dioxide If this explanation is correct the free energy of formation of the metastable oxide from the stable oxide should be found to be about +7500 - 5T cal/mole (auth)

Kinetics and thermodynamics of decomposition of barium carbonate

Abstract: The equilibrium vapour pressure of barium carbonate and the vacuum decomposition rates of the (001) face of its single crystal were measured by torsion–effusion and torsion–Langmuir techniques, respectively. The rate of the free surface decomposition reaction was constant for product layers up to about 1 mm thickness. The apparent activation enthalpy of decomposition for the reaction BaCO3(s)= BaO(s)+ CO2(g) is 225.9 kJ mol–1, which is less than the enthalpy of the equilibrium reaction, 252.1 kJ mol–1. The apparent activation entropy for the reaction is 53.5 J mol–1 K–1. This entropy is also less than the entropy of the equilibrium reaction, 146.6 J mol–1 K–1 in the temperature range studied. These results are shown to be consistent with theoretical predictions if condensed phase diffusion or a surface step prior to desorption is rate limiting.

Die Sublimation und thermische Zersetzung von TeJ4 und die Existenz von TeJ2 in der Gasphase

Abstract: Die Sublimation und thermische Zersetzung des TeJ4 wurde untersucht. Es ergeben sich fur die Sublimation: und Fur die thermische Zersetzung: wurden ΔH° = 19,6 ± 0,8 kcal und ΔS° = 35,9 ± 1 cl erhalten, wahrend fur die Reaktion ΔH° = 14,9 ± 1,5 kcal und ΔS° equals; 30,6 ± 2 cl berechnet, wurden. Durch Gleichgewichtsmessungen und Experimente zum chemischen Transport von Te mit Jod wurde die Anwesenheit von TeJ2 in der Gasphase nachgewiesen. The Sublimation and the Thermal Decomposition of TeJ4 and the Existence of TeJ2 in the Gaseous Phase The sublimation and the decomposition of TeJ4 have been investigated. For the sublimation and the decomposition reactions and the values of enthalpy and entropy were derived (see „Inhaltsubersicht”). The existence of TeJ2 in the gaseous phase was demonstrated by equilibrium measurements and chemical transport experiments.

Urea‐formaldehyde resins: NMR study on base‐catalyzed reaction of formaldehyde with urea in deuterium oxide

Abstract: High-resolution nuclear magnetic resonance (NMR) has been used in order to investigate the base-catalyzed reaction of formaldehyde with urea in deuterium oxide. The effects of temperature and concentration on the chemical shift of glycol species in formalin under basic conditions was investigated. Assignment of all the signals appearing in the addition reaction was completed. The formation of N,N-dimethylolurea, uron, monomethyloluron, and dimethyloluron was observed for the first time, as well as the formation of monomethylolurea, N,N'-dimethylolurea, and trimethylolurea, which had been observed previously: the formation of presumptive tetramethylolurea could not be observed. The rate constants and equilibrium constants for urea, monomethylolurea, N,N'- and N,N-dimethylolurea, and trimethylolurea were estimated by analysis of the decomposition reactions of monomethylolurea and N,N'-dimethylolurea.

Phosphaadamantanes: reaction with formaldehyde in acid solution

Abstract: The compound 1,3,5-triaza-7-phosphaadamantane (PAA) ( 7 , 2) resembles the repeating unit proposed for a wellknown flame retardant polymer prepared from sodium hydroxide-neutralized tetrakis(hydroxymethy1)phosphonium chloride solutions (THPOH) and ammonia. Recently, both the THPOH-NH3 polymer and PAA were found to "decompose" in hot formalin, whereas the oxidized polymer and 1,3,5triaza-7-phosphaadamantane 7-oxide (PAAO) were stable to solutions of hot formalin (3). The only product isolated from the reaction with the polymer or PAA was tris(hydroxymethy1)phosphine oxide. We now have isolated the products from the reactions of phosphaadamantanes with formaldehyde in the presence of an acid. Initially, hexamethylenetetramine picrate was reacted with formaldehyde. With nuclear magnetic resonance spectroscopy (NMR) the work of Foss et al. ( 4 , 5) was confirmed, and a methopicrate salt was proved to be the only product from such a reaction. The product had been identified as a dimethylpentamethylenetetramine picrate (6, 7). The NMR spectra showed a 1:6 ratio of aromatic protons to methylene protons. The use of dimethyl sulfoxide as a solvent interfered with the integration of the methyl protons. This same reaction with PAA and PAAO picrate also produced methopicrate salts as shown by NMR spectroscopy and chemical analyses. The highest theoretical yield of the PAA methopicrate, 45 YO (based upon PAA) (V), also suggested that the decomposition reaction with formaldehyde might also be operative. Yields of this reaction with hexamethylenetetramine and PAAO were 67 (IV) and 73% (VI), respectively. The reaction of PAAO with formaldehyde in the presence of another strong acid, hydrochloric, produced a methochloride salt (VII). Apparently, acid strength is important since in the presence of acetic acid, the reaction with either PAA or PAAO produced only the starting compounds. The methopicrates of hexamethylenetetramine, PAA, and PAAO were also prepared in quantitative yield from methyl iodide salts of the three compounds and sodium picrate. The compound 2-thia-1,3,5-triaza-7-phosphaadamantane 2,a-dioxide did not react with formaldehyde in the presence of either picric or hydrochloric acid. However, the picrate and chloride were isolated and by NMR spectroscopy shown to be ammonium salts. This work substantiates earlier work that PAA and PAAO resemble hexamethylenetetramine in their chemistry, that is, they are nitrogen oriented and that PAS02 is phosphorus oriented. Elemental analyses obtained were in agreement with theoretical values and were submitted for review.

Effect of diluent and atmosphere on DTA peaks of decomposition reactions

Abstract: A study has been carried out of the influence of sample dilution, the nature of the gas atmosphere, and the static or flowing conditions of this, on the DTA curves resulting from the thermal decomposition of solids. The results obtained seem to indicate that only the reversible reactions of solid thermal decomposition are seriously affected by such factors.

Acetylation of ferrocene. Monitoring a chemical reaction by high pressure liquid chromatography

Abstract: The authors wish to describe how HPLC can be used to follow the course of a decomposition reaction.

Reaction of 1,3-dienes with sulphur dioxide. Part 1. Thermal decomposition of 2,5-dihydrothiophen 1,1-dioxides

Abstract: Rates of decomposition of 18 substituted dihydrothiophen 1, 1-dioxides in solution (to yield the corresponding butadiene and SO2) are reported, together with activation parameters and solvent and isotope effects. Rates are mildly accelerated by +M groups at C-3 and by alkyl substituents at C-2 but sterically retarded by bulky groups at C-3 and especially by two β-substituents. 3, 4, 5, 6-Tetrahydro-1H-cyclopenta[c]thiophen 2, 2-dioxide is especially reactive and this is attributed to strain release during fragmentation. The reactions accord in general with requirements for a chelotropic reaction.

Self-heating in the decomposition of 3-methyl-3-chlorodiazirine: determination of reaction exothermicity and correction of arrhenius parameters

Abstract: The gas-phase decomposition of 3-methyl-3-chlorodiazirine(I) has been re-investigated using direct measurement of the reactant gas temperature to demonstrate the occurrence of self-heating during reaction. In addition, the thermal conductivity of (I) has been measured at 298 and 348 K. From these data ΔH°f(I) is determined as 55.6 ± 9.5 kcal mol–1 and a significant error in the earlier measurement of the Arrhenius parameters for the low pressure decomposition reaction is corrected.

The thermal decomposition of simple carbonate esters

Abstract: Wahrend Dimethylcarbonat sich bis zu 390°C nicht zersetzt, zersetzen sich Athyl-methyl-, Diathyl-, Athyl-propyl-, Dipropylcarbonat zwischen 300-400°C mit ahnlichen Geschwindigkeiten zu CO2, Alken und Alkohol.

Thermal decomposition of potassium azide

Abstract: Experimental studies of the thermal decomposition of single crystal and powder samples of KN3 in an ultrahigh vacuum environment are reported. Mass spectrographic detection was used to monitor the decomposition products and, from the temperature dependence of the N2 partial pressure, three regions of decomposition were found with associated activation energies of 1.0±0.1, 1.35±0.05, and 2.4±0.2 eV in order of increasing temperature. Azide radicals and potassium atoms were also detected in the decomposition products. The application of an electric field across the sample during decomposition was found to increase the decomposition rate for both signs of the voltage on the free surface of the crystal. The relaxation time for the pressure change associated with application of the field was found to be essentially the same as that for the decay of the induced ionic current to an equilibrium value. Models for the decomposition process are discussed.

Apparatus for decomposing organic matter

Abstract: PURPOSE:To efficiently perform catalytic heat decomposition reaction and to regenerated the catalyst for repeated use by contacting material to be decomposed such as polymers or N-containing organic compounds with a catalyst made of metals (or alloy) of VIII group.

Fourier analysis for correction of thermograms obtained with a heat flow microcalorimeter of high stability (for adsorption and decomposition study)

Abstract: A description is given of a heat flow microcalorimeter designed to study the adsorption of vapours on solids and their subsequent decomposition reaction rates. The usefulness of electrical analogues in finding stability improvements is stressed. The thermograms being necessarily distorted by thermal inertia may be corrected by means of Fourier analysis. The performance of Fourier analysis is traced for a number of test experiments.

DECOMPOSITION REACTIONS OF UNSATURATED α-PHENYLSULFONYL-α-DIAZO KETONES

Abstract: Thermal decomposition of unsaturated α-phenylsulfonyl-α-diazo ketones afforded various types of cyclization products derived from the phenylsulfonylketene intermediates, along with ones from the usual ketocarbene intermediates, which are dependent closely on the position and alkyl substitution of the olefinic parts.

The chemistry of uranium. xiv. the thermal stability of some actinoid nitrates

Abstract: The thermal decomposition of Cs2 U(NO3)6 has been investigated. The activation energy for the decomposition reaction was estimated to be ±120 kJ/mole, while the enthalpy of the reaction was calculated as 18 kJ/mole. These energy parameters were compared with similar parameters obtained for the decomposition of Cs2 Th(NO3)6 and U(NO3)4.2hmpa. It indicated that the nitrate ion is primarily responsible for the oxidation of the uranium with atmospheric oxygen having no effect at all. The dissociation reactions involved in the decomposition of M(NO3)4.4hmpa, (M = U and Th), are accompanied by intramolecular rearrangements of the nitrate groups.

The decomposition of dimethylbenzylanilinium chloride in alcoholic solvents

Abstract: The decomposition of dimethylbenzylanilinium chloride (DMBAC) was found to follow second-order kinetics in ethanol or aqueous ethanol solvents, but first-order kinetics in higher alcoholic solvents From the activation parameters obtained at 80 °C, different isokinetic relationships were found for the ethanol series and the higher alcohol series The dissociation constants of DMBAC in ethanol and isopropanol at 80 °C were calculated to be 734 × 10−3 and 210 × 10−4 mol/l, respectively, from conductivity measurements Accordingly, it was concluded that in higher alcohols the major part of DMBAC exists as ion pairs, which are responsible for the decomposition reaction, but in ethanol the decomposition involves a bimolecular reaction between free ions

Low temperature deposition of metal nitrides by thermal decomposition of organometallic compounds

Abstract: Decomposition reaction of dialkylamides of boron, silicon, tin, titanium, zirconium, niobium, and tantalum was investigated. The amides of transition metals decomposed to the corresponding nitrides at 300~176 whereas those of boron, silicon, and tin yielded elemental deposits at higher temperatures. In the deposition of titanium nitride from titanium tetrakis(dimethylamide), two optimum temperatures at 400 ~ and at 800~ in nitrogen or hydrogen atmosphere were found, but in argon only low temperature deposition was possible. The low and high temperature processes are discussed in relation to mass spectral analysis of the exhaust gases formed at various decomposition temperatures of titanium amide. Metal nitrides are well known to have outstanding physical and chemical properties and have been prepared by the reactions of metal halides or hydrides with nitrogen + hydrogen or ammonia, or of metals with nitrogen (1). These reactions usually require temperatures higher than 1000~ which have limited the application of the nitrides as the useful coatings on many materials. Therefore, their preparation at lower temperature, where deformation of substrate materials can be avoided, should be important.

Thermogravimetrie von Styrol—Chloranilcopolymeren

Abstract: The thermal decomposition of styrene-chloranil copolymers is investigated by dynamic thermogravimetry. The decomposition occurs at relatively low temperatures and is correlated to the chemical structure of the polymers.

Self-heating in the decomposition of 3-methyl-3-chlorodiazirine- determination of reaction exothermicity and correction of arrhenius parameters

Abstract: The gas-phase decomposition of 3-methyl-3-chlorodiazirine(I) has been re-investigated using direct measurement of the reactant gas temperature to demonstrate the occurrence of self-heating during reaction. In addition, the thermal conductivity of (I) has been measured at 298 and 348 K. From these data ΔH°f(I) is determined as 55.6 ± 9.5 kcal mol–1 and a significant error in the earlier measurement of the Arrhenius parameters for the low pressure decomposition reaction is corrected.

Thermal decomposition of trimethylene sulfone and 3-methyl sulfolane

Abstract: Trimethylene sulfone and 3methyl sulfolane have been pyrolyzed using a modification of the toluene flow method and a comparative rate technique. The main decomposition reactions are where k1=1016.1±0.3 exp(−28,100±500/T) sec−1 and k2=1016.1±0.4 exp(−33,200±750/T) sec−1.

Reaction of isocyanide-mercuric chloride complexes with active methylene compounds

Abstract: Isocyanide-mercuric chloride complexes, which were obtained from isocyanides and mercuric chloride, react readily with active methylene compounds in the presence of triethylamine giving 2 : 1 adducts. The adducts were formed through a redox decomposition reaction of the complexes accompanying with the formation of metallic mercury. The reaction of the adducts was also investigated.