Kinetics of decomposition

Chemical Properties. The kinetics of decomposition of OF2 by pyrolysis in a shock tube are different, as a result of surface effects, from those obtained by conventional decomposition studies. Dry OF2 is stable up to 250°C (22). 

Oxygen Difluoride as a Source of the OF Radical. The existence of the OF radical [12061 -70-0] was first reported in 1934 (27). This work was later refuted (28). The OF radical was produced by photolysis of OF2 in a nitrogen or argon matrix at 4 K. The existence of the OF species was deduced from a study of the kinetics of decomposition of OF2 and the kinetics of the photochemical reaction (25,26) ... 

Nifurtoinol. Treatment of nitrofurantoin with formaldehyde gives nihirtoinol, 3-hydroxymethyl-l-[5-nitro-2-furanyl)methyleneamino]-2,4-imidazohdinedione, a urinary tract antibacterial (46). The kinetics of decomposition of this dmg and its potential as a prodmg of nitrofurantoin have been reported (47). 

There have been numerous studies on the kinetics of decomposition of A IRK. AIBMe and other dialkyldiazenes.46 Solvent effects on are small by conventional standards but, nonetheless, significant. Data for AIBMe is presented in Table 3.3. The data come from a variety of sources and can be seen to increase in the series where the solvent is aliphatic < ester (including MMA) < aromatic (including styrene) < alcohol. There is a factor of two difference between kA in methanol and k< in ethyl acetate. The value of kA for AIBN is also reported to be higher in aromatic than in hydrocarbon solvents and to increase with the dielectric constant of the medium.31 79 80 Tlic kA of AIBMe and AIBN show no direct correlation with solvent viscosity (see also 3.3.1.1.3), which is consistent with the reaction being irreversible (Le. no cage return). 

CA, not found 7) J. Smid M. Szwarc, Kinetics of Decomposition of Iso-Butyryl Peroxide and Reactions of Iso-Propyl Radicals , Syracuse Univ, NY, contract DA-30-115-ORD-678 (1958) 8) H.T. Lee et al, Evaluation of... 

Compression of powder samples into pellets can also influence the kinetics of decomposition [97,391—393], mainly through hindering the escape of reaction products. 

The kinetics of decomposition of these solids may be classified according to the process which has been identified as rate-limiting. This criterion allows a more concise presentation but is not completely satisfactory since some reactions show a sensitivity of behaviour to the conditions prevailing [1270]. Furthermore, certain of the reactions discussed are reversible. Reference to the extensive literature devoted to the thermodynamic properties of these solids and phase stabilities and interactions will only be made where kinetic observations or arguments have been used. 

It is appropriate to start with BaN6 since this compound has been studied particularly intensively and has been regarded as a model in the development of the theory of kinetics of decompositions of solids. The sigmoid a—time curves for BaN6 pyrolyses, Fig. 15, are typical examples of solid state autocatalytic behaviour. 

Hi) Cobalt formate. There is evidence that the kinetics of decomposition of cobalt formate [1026,1027] are similar to those of the nickel salt, considered in some detail below. A significant point of difference, however, is that metal production during reaction of the former is preceded by formation of cobalt oxides [1028]. 

The literature available constitutes neither a comprehensive nor a particularly systematic investigation of the kinetics of decompositions of metal carboxylates. (A comparable remark could also be made at the end of each of the Sections 1—4 and 6.) The simplest reactants have naturally been accorded the greatest interest. Reactions of certain formates and... 

Isothermal studies at 370—420 K have been made of the kinetics of decomposition of [Co(NH3)6](N3)3, [Co(NH3)5(N3)](N3)2 and both cis-and frarcs-[Co(NH3)4(N3)2](N3) [1120]. Results are interpreted as indicating the operation of a common reaction mechanism which is not greatly influenced by either the constituents or the stereochemistry of the complex cation. The reactions of all four compounds may yield either CoN or Co(NH3)2(N3)2 as the residual product the alternative decompositions may be represented as... 

Comparative studies [1127] of the kinetics of decomposition of similar salts containing related pyridine ligands have been used to investigate the strength of M—N bonds in coordination compounds. Non-isothermal DSC measurements were used to determine values of E for the reactions... 

Numerous and varied conclusions have been stated explicitly or implied in the text of Chaps. 2—5. These include mechanistic deductions, references to inconsistencies or irreconcilable interpretations found in different studies, recommendations for the re-analysis of certain experimental data etc. These will not be repeated in detail in the present chapter, which summarizes only the most significant and general conclusions relating to the kinetics of decompositions and interactions of solids. 

Prokopczyk B, Bertinato P, Hoffmann D. 1988. Synthesis and kinetics of decomposition of 7-(2-cyanoethyl) guanine and 6-(2-cyanoethyl) guanine, markers for reaction of acrylonitrile and 3-(methylnitrosamino) propionitrile with DNA. Carcinogenesis 9 2125-2128. 

Other workers have used the tristimulus parameters to study the kinetics of decomposition reactions. The fading of tablet colorants was shown to follow first-order reaction kinetics, with the source of the illumination energy apparently not affecting the kinetics [49]. The effect of excipients on the discoloration of ascorbic acid in tablet formulations has also been followed through determination of color changes [50]. In this latter work, it was established that lactose and Emdex influenced color changes less than did sorbitol. 

The resulting products, such as sulfenic acid or sulfur dioxide, are reactive and induce an acid-catalyzed breakdown of hydroperoxides. The important role of intermediate molecular sulfur has been reported [68-72]. Zinc (or other metal) forms a precipitate composed of ZnO and ZnS04. The decomposition of ROOH by dialkyl thiophosphates is an autocata-lytic process. The interaction of ROOH with zinc dialkyl thiophosphate gives rise to free radicals, due to which this reaction accelerates oxidation of hydrocarbons, excites CL during oxidation of ethylbenzene, and intensifies the consumption of acceptors, e.g., stable nitroxyl radicals [68], The induction period is often absent because of the rapid formation of intermediates, and the kinetics of decomposition is described by a simple bimolecular kinetic equation... 

Autocatalytic decomposition can be determined by 1ST techniques. The sensitivity of 1ST equipment enables measurements to be made at relatively low temperatures, which results in the potential to examine a wide temperature range. This is an advantage because extrapolations outside the temperature range actually examined in tests are reduced. The importance here is that the kinetics of decomposition at high temperatures are not always the same as at the lower temperatures of likely processing. 

The kinetics of decomposition of certain inorganic oxides and sulphides and a few related compounds are reviewed in this chapter. Discussion is limited to the gas and liquid phase and to the reactions of neutral species. Accordingly, reactions in ionizing solvents have been excluded. The decompositions of the following compounds are considered C302, CO, C02, CS2, COS, CSe2, COSe, N20,... 

Rolla, E., and C.L. Chakrabarti, Kinetics of Decomposition of Tetrathionate, Trithionate and Thiosulphate in Alkaline Media, Enrion. Sci. Technol., 16, 852, 1982. 

There are comparatively few studies addressing the structure-metabolism relationships of phosphoric acid monoester hydrolysis. For example, kinetics of decomposition in rat whole blood were examined for the phosphoric acid monoesters of estrone, 17a- and 17/J-testosterone, 3-(hydroxyme-thyl)phenytoin (see Fig. 9.7,a), and 1-phenylvinyl alcohol (9.28, the enolic form of acetophenone) [87]. As a general trend, the rate of hydrolysis increased with the acidity of the leaving hydroxylated compound. In other words, hydrolysis was the fastest for the phosphoric acid aryl monoester (estrone 3-phosphate), and slowest for the two testosterone phosphoric acid... 

C.M. Slander, Kinetics of decomposition of magnesium hydride, J. Inorg. Nucl. Chem. 39 (1977) 221-223. 

A method for determination of peroxynitrite down to subnanomolar concentrations is based on CL in the presence of luminol (124, Scheme 3). The kinetic of decomposition of peroxynitrite according to equation 119 is a function of pH and can be measured in a FIA system. The solution carrying the analyte is mixed in the CL cell with 124 dissolved... 

Its kinetics of decomposition differs from those of other possible intermediates. 

The mechanisms and kinetics of decomposition of the transient complexes LmM + 1-R in aqueous solutions depend on the nature of the central cation, of the ligands, L, of the substituents on the aliphatic residue, R, on the pH and on the presence and nature of various substrates, S, in the medium, e.g., 02. In the following section the major mechanisms observed are discussed. 

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