Decomposition chemistry

Chemical Properties. Anhydrous sodium dithionite is combustible and can decompose exothermically if subjected to moisture. Sulfur dioxide is given off violentiy if the dry salt is heated above 190°C. At room temperature, in the absence of oxygen, alkaline (pH 9—12) aqueous solutions of dithionite decompose slowly over a matter of days. Increased temperature dramatically increases the decomposition rate. A representation of the decomposition chemistry is as follows ... 

Accelerating rate calorimeters (ARC) are customarily used to determine the overall reactivity of compounds. One limitation of these instruments is that pressure data at pre-exotherm temperatures are not recorded. However, such information may be important for the analysis of reactive systems in which pressure events are observed prior to the exotherm. An ARC has been modified so that pressure data can be acquired and stored for kinetic analysis by interfacing with a personal computer. Results are presented using this technique for the study of the decomposition chemistry of 4,4 -diisocyanatodiphenylmethane (MDI). 

Golchin A, Baldock JA, Oades JM (1998) A model linking organic matter decomposition, chemistry, and aggregate dynamics. In Lai R, Kimble JM, Follett RF, Stewart BA (eds). Soil processes and the carbon cycle. CRC Press, Boca Raton, pp 245-266... 

Films at NASA GRC were deposited using homemade spray or aerosol-assisted chemical vapor deposition (AACVD) reactors to exploit the lower deposition temperature enabled by the simpler decomposition chemistry for the SSPs.6 9 AACVD is a simple and inexpensive process that offers the advantage of a uniform, large-area deposition, just like metal organic CVD (MOCVD), while also offering the low-temperature solution reservoir typical of spray pyrolysis methods. 

DECOMPOSITION CHEMISTRY OF HIGH-ENERGY-DENSITY FUELS BY FLOW TUBE MASS SPECTROMETRY... 

Beard, B.C. (1995) Early decomposition chemistry of NTO, in Proc. 10th (Inti.) Symp.on Detonation (eds J.M. Short and D.G. Tasker), Office of Naval Research, Arlington, VA.USA, pp. 204-207. 

Discussion of the decomposition chemistry of formyl complexes has been deferred until this stage because some of the reactivity modes described in Section IV can play important roles. 

Hiickel MO calculations have not revealed any intrinsic kinetic barrier to hydride migration to coordinated CO (93). Thus it is worthwhile to consider possibilities that might mask the occurrence of a metal hydride carbonylation reaction. For instance, metal hydrides have been observed to react rapidly with metal acyls reduction products such as aldehydes or bridging —CHRO— species form (94-96). Therefore, it is possible that a formyl complex might react with a metal hydride precursor at a rate competitive with its formation. Such a reaction could also complicate the decomposition chemistry of formyl complexes. Preliminary studies have in fact shown that metal hydrides can react with formyl complexes (35, 57), but a complete product analysis has not yet been done. 

Decomposition chemistry of the azo compounds is potentially complicated by the existence of cis and trans isomers (23 and 24). The trans form is the more... 

This molecule is unstable, with incredibly high maximum rates of temperature and pressure rise calorimetrically determined (14,000°C and 1,500 bar per min) even though dissolved in a solvent. Several pages of computerised fantasy over the heat of decomposition, based solely on identified, but unquantified, volatiles while neglecting the black tar which is probably the major product, leave readers no wiser as to the circumstances. The original reactor-burst during manufacture from the alcohol and the sulfonyl chloride in the unspecified solvent should have started at around room temperature this formation reaction is presumably exothermic. The usual solvents for such reactions, tertiary amines, would also be important reagents in decomposition chemistry. 

As mentioned earlier, at 500° C and 34.5 MPa supercritical water has a small dielectric constant, a very low ion product, and behaves as a high temperature gas. These properties would be expected to minimize the role of heterolysis in the dehydration chemistry. As shown in Table 1, the conversion of ethanol to ethylene at 500° C is small, even in the presence of 0.01M sulfuric acid catalyst. The appearance of the byproducts CO, C02) CH i+ and C2H6 points to the onset of nonselective, free radical reactions in the decomposition chemistry, as would be expected in the high temperature gas phase thermolysis of ethanol. 

The initial decomposition chemistry involves unimolecular reactions. This was the conclusion of the first gas-phase kinetics study [84] and has been repeatedly confirmed by subsequent bulb and shock-tube experiments [85, 86]. That first study used shock heating to induce thermal decomposition [84], The data were interpreted in terms of simple C-N bond fission to give CH2 and N02. A more extensive and definitive shock-tube study was reported by Zhang and Bauer in 1997 [85]. Zhang and Bauer presented a detailed kinetics model based on 99 chemical reactions that reproduced their own data and that of other shock-tube experiments [84, 86]. An interesting conclusion is that about 40% of the nitromethane is lost in secondary reactions. 

Zhang L, Carman AJ, Casey SM (2003) Adsorption and thermal decomposition chemistry of 1-propanol and other primary alcohols on the Si(100) surface, J. Phys. Chem. B 107 8424-8432... 

Reaction 5. Another aspect of the reaction chemistry of Mn(III) is demonstrated by the classic kinetic studies of the decomposition chemistry of manganese (III) oxalate complexes (35, 36). These studies derive from an earlier discussion of the synthesis of manganese (III)-oxalate compounds (37). A similar set of kinetic and synthetic investigations, have been summarized for the manganese (III )-malonate complexes (38, 39). Both sets of studies confirm that Mn(III) has a particularly strong... 

CH2Ph)]. The former is an unusual 13-electron species whose coordinative unsaturation makes it an extremely effective catalyst for ethylene polymerization, and which exhibits a rich thermal decomposition chemistry. The latter, a mixed-valent complex exhibits ferromagnetic coupling between the two chromium atoms and is a catalyst for the polymerization of ethylene as well. ... 

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