Primary decomposition products

The initial and primary decomposition product for BPDA-PDA is a negative ion fragment with m/z = 229. The chemical structure associated with the 229 ion has not yet been assigned. Product-formation by pyrolysis decomposition of... 

The successful and possibly rapid degradation of toxic dye residues is of considerable importance form both a human and a veterinary toxicological point of view and for environmental protection. Because of the high amount of dyes loaded in the environment, much effort has been devoted to the development of physical, physicochemical and microbiological methods obtaining the degradation of dyes to non-toxic (even nutritive) derivatives. As has been previously mentioned, visible spectroscopic methods are widely applied for the measurement of the decomposition rate of dyes. However, when more than one dye molecule is simultaneously present or the primary decomposition products also absorb on... 

The PCC oxidation of 3-amino-4,5-diphenyl-2(3//)-oxazolone 96 affords mono-diazobenzyl 286 as the primary decomposition product obtained via loss of carbon monoxide from the postulated A -nitrenolactam 285. Oxidation of 96 with tert-BuOCl/NEt3 at 108 °C results in a deep green solution of 285, which reacts with dimethyl sulfoxide (DMSO) to give the sulfoximide 288 (Fig. 5.68). ... 

From the decomposition mechanism and the products formed it can be deduced that DCP primarily generates cumyloxy radicals, which further decompose into highly reactive methyl radicals and acetophenone, having a typical sweet smell. Similarly, tert-butyl cumyl peroxide (TBCP) forms large quantities of acetophenone, as this compound still half-resembles DCP. From the decomposition products of l-(2-6 rt-butylperoxyisopropyl)-3-isopropenyl benzene ( ), it can be deduced that the amount of aromatic alcohol and aromatic ketone are below the detection limit (<0.01 mol/mol decomposed peroxide) furthermore no traces of other decomposition products could be identified. This implies that most likely the initially formed aromatic decomposition products reacted with the substrate by the formation of adducts. In addition, unlike DCP, there is no possibility of TBIB (because of its chemical structure) forming acetophenone. As DTBT contains the same basic tert-butyl peroxide unit as TBIB, it may be anticipated that their primary decomposition products will be similar. This also explains why the decomposition products obtained from the multifunctional peroxides do not provide an unpleasant smell, unlike DCP [37, 38]. 

It appears, therefore, that in this case the primary decomposition product is phenol and that by coupling with undecomposed diazonium salt it is converted into the azophenol. Addition of zinc oxide to the reaction mixture raises the yield of phenol to 60% while that of the azo compound falls to approximately 30%. 

If all equilibria were established quickly during decomposition of the salts, N2 and 02 would be the only gaseous components however, the reaction N02 = 1/2 N2 + 02 is very slow below 1000 K thus, if N02 is the primary decomposition product, it will not decompose appreciably by this reaction and only the equilibrium NO + 1/2 02 = N02 needs to be considered. 

The high ratio of biphenyl to naphthalene may reflect a contribution from a second path, via the primary decomposition product in stepwise loss of carbon dioxide and carbon monoxide, paralleling the reaction sequence known to occur under electron impact. The intermediate species (11) could add to benzene to give biphenyl by subsequent loss of carbon monoxide or fluorenone by ring closure and loss of hydrogen ... 

Polysaccharide pyrolysis at 375-520°C is accompanied by a higher rate of weight loss and evolution of a complex mixture of vapor-phase compounds preponderantly of HsO, CO, C02, levoglucosan, furans, lactones, and phenols (Shafizadeh, 1968). The volatile and involatile phase compositions are conditional on the rate of removal of the vapor phase from the heated chamber (Irwin, 1979), inasmuch as the primary decomposition products are themselves secondary reactants. The reaction kinetics is described as pseudo zero order (Tang and Neill, 1964) and zero order initially, followed by pseudo first order and first order (Lipska and Parker, 1966), suggesting an... 

The primary decomposition product [115] is assumed to lose vinyl alcohol and a hydrogen atom to give a key fragment of mass 96, [115]->[117]->[118].62... 

Cleavage of the primary decomposition product [115] with loss of cyclopropanol yields an ion of mass 83, which is stabilized by elimination of a hydrogen atom, [115]->[122]->[123]. 

Pyrolysis gas chromatography can be used to determine the acrylonitrile content of the SAN copolymer [7-9]. It is a method that heats the polymer above the decomposition temperature, then separates and identifies the low molecular weight compounds formed. The primary decomposition products are styrene, acrylonitrile, and propionitrile, and the styrene content of the copolymer is directly proportional to the styrene yield from pyrolysis [8]. 

Slow decomposition of PTFE occurs above the application temperature of 260°C. However, for a noticeable decomposition to occur, temperatures above 400°C are needed. The primary decomposition products are tetrafluoroethylene (TFE) and difluorocarbon diradicals (CF2). Further products are formed by secondary reactions, depending on temperature, reaction pressure and reaction atmosphere. The typical main products are TFE, hexafluoropropene (HEP), cyclo-perfluorobutane (C-C4F8) and other fluorocarbons. Most of these substances are nontoxic, but highly toxic substances such as perfluoroisobutene or fluorophosgene are also formed under some reaction conditions. 

Metaldehyde is readily absorbed from the gastrointestinal tract. Metaldehyde s primary decomposition product in the body is acetaldehyde. Metabolites can cross the blood-brain barrier and enter the central nervous system. 

COFj has been detected as a primary decomposition product of high stability, non-flammable, carboxynitroso rubber [1122]. The use of carboxynitroso rubber as a fire-resistant furnishing material in enclosed habitable spaces that are subject to restricted ventilation e.g. aircraft) is thus to be strongly discouraged. 

The analysis of the primary decomposition products from the decomposition of methyl-cyc/o-pentane requires the addition of only a few reactions to the scheme shown in Fig. 6. Three methyl-cyc/o-pentyl radicals were already formed from the successive isomerization reactions of cyc/o-hexy 1-radical, and thus only the tertiary radical, with its isomerization and decomposition reactions to form methyl-allyl radical and ethylene, needs to be included... 

Fig. 5 shows the rate of production of volatile compounds from starch and from D-glucose. It is apparent that furan and 2-methylfuran are initially produced in largest proportion, although this is not true of the summative yields in Table V. Again, although the total yields of acetaldehyde and acetone are each comparable to those of the furans, the initial rate of production is much less, but it does not decrease so much with time. These observations suggested that furan and its derivatives may be the primary decomposition products this hypothesis is discussed on p. 506. 

The methods used up to now to investigate the mechanism of decomposition reactions generally allow only the determination of the decomposition products in the gas phase, which might have been formed by reactions of the primary decomposition products on the catalyst or in the gas phase. In the decomposition of formic acid on a nickel catalyst, investigated only at higher temperatures, the formation of hydrogen and carbon dioxide is observed, but this is not an exact proof that the decomposition follows the equation... 

To find the primary decomposition products at low temperatures, a method should be used by which a reaction even of a monolayer may be observed and that in a manner characteristic for the molecules in question. A method appropriate for the investigation of the elementary processes of decomposition reactions is to produce the electrically conducting catalyst in form of a transparent film under the evaporation and to study the change of its resistance by influence of the decomposing molecules. Hereby the electric resistance R of the film decreases or increases, the product molecules transferring electrons to the surface of the film or receiving electrons from it, as the case may be (I). On adsorption of hydrogen (J, ), (Fig. 1), water vapor ( , 3) (Fig. 2), or carbon dioxide (3), (Fig. 3), the resistance of the nickel layer decreases. On adsorption of carbon monoxide, however, (2, 3), (Fig. 4), it increases. 

Diamminediazidocopper(II), [(NH3)2Cu (N3)2] , the primary decomposition product of the above complex, was formerly considered the azide salt of a cationic complex [188], i.e., of the composition [(NH3)2Cu ] (N3)2,but its chemical behavior [190] and crystal structure [191] support the constitution of a neutral azido complex. It is a blue, crystalline solid which is insoluble in water. The compound deflagrates on friction or impact. In a flame it explodes violently after apparently first decomposing to Cu(N3)2, which is suggested by the color change and its temperature of explosion (202°C). 

Basolo et al, have also reported (36) their investigations of the add-catalyzed decomposition of coordinated azide. They find that the primary decomposition product is a protonated nitrene... 

Method In accordance with the general concept of the approach, based on the CDV mechanism, the goal of thermochemical analysis is to find out the composition of the primary decomposition products, for which the magnitude of the reaction molar enthalpy is taken to be the E value. The fundamental difference between the commonly accepted approach and the thermochemical approach is illustrated schematically in Fig. 9.1. 

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