Decomposition sequence

Figure 1 shows the decomposition sequence for several hydrous precursors and indicates approximate temperatures at which the activated forms occur (1). As activation temperature is increased, the crystal stmctures become more ordered as can be seen by the x-ray diffraction patterns of Figure 2 (2). The similarity of these patterns combined with subtie effects of precursor crystal size, trace impurities, and details of sample preparation have led to some confusion in the Hterature (3). The crystal stmctures of the activated aluminas have, however, been well-documented by x-ray diffraction (4) and by nmr techniques (5).

Diaryl pyrrolopyrroles (DPPs), 79 441-443 commercial, 79 443t Diarylthallium(III) derivatives, 24 634 Diaspore, 2 345t, 347, 426 classification, 2 422 decomposition sequence, 2 392, 421 mineralogical and structural properties of, 2 423t... 

Hydrotreating catalysis, molybdenum compounds in, 17 37-38 Hydro trioxides, 18 435-436 Hydrotrioxides, formation of, 17 784. See also Hydrogen trioxide Hydrotropes, cosmetic surfactants, 7 834t Hydrous aluminas, decomposition sequence, 2 392... 

Norbornene-ethene copolymer, 16 113 Norbornene-ethylene copolymers, 20 433 physical properties of, 20 420-422 Norbornenodiazetine derivatives, 13 306 Nordel IP (metallocene), 7 637 Nordihydroguaiaretic acid, antioxidant useful in cosmetics, 7 830t Nordstrandite, 2 421, 425 activation, 2 394 classification, 2 422 decomposition sequence, 2 392 from gelatinous boehmite, 2 427 structural properties of, 2 423t NO-reduction reactions, TWC catalyst, 10 49... 

The commercially available form of Aspartame is hemihydrate Form II, which transforms into hemihydrate Form I when milled, and a 2.5-hydrate species is also known [57,58]. XRPD has been used to study the desolvation and ultimate decomposition of the various hydrates. When heated to 150°C, both hemihydrate forms dehydrate into the same anhydrous phase, which then cyclizes into 3-(carboxymethyl)-6-benzyl-2, 5-dioxopiperazine if heated to 200°C. The 2.5-hydrate was shown to dehydrate into hemihydrate Form II when heated to 70°C, and this product was then shown to undergo the same decomposition sequence as directly crystallized hemihydrate Form II. 

K. J. D. MacKenzie and R. H. Meinhold, Al and Mg solid-state magic-angle spinning nuclear magnetic resonance study of hydrotalcite and its thermal decomposition sequence. /. Mater. Chem., 1993, 3,1263-1269. 

As expected, there is a general tendency for the nucleophile to attack the a position. This preference is preserved even when a methoxy group occupies a fi position (formation of 133 from 2-nitro-3-methoxythiophene). H-NMR evidence indicates that in methanol solution an adduct at C-2 of 2-methoxy-5-nitrothiophene (134) is formed as an intermediate in a decomposition sequence probably involving ring opening.176 However, in DMSO no evidence of such an adduct was recorded.17... 

The precise transition temperatures might depend on the presence of the necessarily coadsorbed Cl atoms, but the decomposition sequence is probably independent of this. 

Mass spectra of hydroxy- and alkoxy-coumarins have been very intensively studied. The decomposition sequence of 3-hydroxycoumarin is initiated by carbon monoxide loss from the molecular ion giving a 2-hydroxybenzofuran ion. Subsequent fragmentation occurs by two major pathways, involving a further loss of CO and expulsion of a formyl radical. The former leads to the base peak, and thence by another loss of CO to give the abundant benzene radical cation at m/e 78. The other main pathway gives a benzoyl cation which leads to the phenonium ion at m/e 77 (77IJC(B)816). 

Grandy, A. S., and Neff, J. C. (2008). Molecular C dynamics downstream The biochemical decomposition sequence and its impact on soil organic matter structure and function. Sci. Total Environ. 404(2/3), 297-303. 

No solid-phase transitions have been reported. The salt begins to decompose noticeably at 410°C. The first step in the decomposition sequence is probably87-88... 

Fio. 3. Decomposition sequence of the C2HsHe+ ion from the decay of C2H5T. The number above each arrow indicates the energy in eV required for the correspondent decomposition. The numbers in parentheses indicate the abundances of the charged fragments (Wexler and Hess, 19S8). 

This ordered set of subgraphs of a graph G is called the expansion of G, or the decomposition-sequence of G. 

Figure 4.9. Changes in the Si MAS NMR spectra during the thermal decomposition of chrysotile (white asbestos). Note the evidence for the two dehydroxylated phases, that at — 72 ppm forming forsterite directly, that at — 97 ppm forming enstatite by the thermal decomposition sequence shown schematically at the right. From MacKenzie and Meinhold, (1994a), by ptermission of copyright owner.

Figure 8.13. MAS NMR spectra of hydrotalcite (Mg6Al2(0H)i6C03.4H20) taken at various stages of its thermal decomposition sequence. Note the loss of the hydrotalcite quadrupolar lineshape and the progressive shift of the resonance line towards the position of MgO.

Figure 3. Decomposition sequence of aluminum hydroxides". Note Enclosed area indicates range of occurrence. Open area indicates range of transition.

An important practical objective for studying the photophysics of the silver halides is to learn to control the light-induced decomposition sequence leading to the formation of the photographic latent image. Structural imperfections have been found to play a critical role in these events through their interactions with excitons and free carriers. 

The thermal decomposition of manganese ) acetate 4-hydrate is discussed (57X to illustrate the use of the self-generated atmosphere. A two-step decomposition sequence has been proposed, similar to the following ... 

The EGA curves of siderite, as determined by GC techniques, were reported by Kubas and Szalkowicz (180). Figure 8.69 gives the EGA. as well as the TG and DTA curves, of siderite, which was heated in a dynamic helium atmosphere. The C02 curve peak, as determined by use of GC. corresponded very well with TG and DTA curve temperatures. There is a small delay in the evolution of CO, which is present even in high-vacuum studies. On the basis of these curves, the decomposition sequence follows the reactions... 

This perturbation can be explained. Indeed, when the pyrolysis of an alkane (yH) involves several stoichiometries, the reaction chain includes several kinds of decomposition sequences such as ... 

The effect of the additives on alumina has been widely studied with respect to the following parameters stabilizing elements, concentrations (0,5 - 20% wt.), type of the precursor (salt, hydroxide, oxide), procedure of introduction, conditions of the subsequent thermal treatment. The controversy in the role and mechanism of various additives is caused by the fact that various researchers use different doping methods and different method producing alumina. Moreover, the term y-alumina is frequently used to designate any transition forms which occur first in the decomposition sequence, i.e. x, P y-AbOa. 

Based on this decomposition sequence, a model was developed (Antolotti et al., 1998 GralSmann and Heimann, 2000 Dyshlovenko et al., 2004a) which showed the in-flight evolution of individual calcium phosphate phases. During the short... 

Ideally, the intermediates and products need to be identified if the reaction mechanisms are to be determined unambiguously. In order to establish a complete picture of the sequence of product formation, the observed or suspected intermediate species need to be studied independently to establish their breakdown pattern and thermal stability. For example, the decomposition sequence for aqueous morpholine, which is used as a pH buffer in the water/steam cycle of many power plants, was studied in this manner and found to involve two independent, complex reaction schemes (one of which yields acetic acid). Each reactive intermediate was identified and its decomposition kinetics studied independently to verify that its decomposition rate was in keeping with the projected overall mechanism for morpholine decom-... 

In the case of lighter rare earths, the respective carbonates decompose through the oxy carbonates Ln202C03 (as indicated by TG), which then decompose endothermically to their respective oxides. However, this step is not observed in the heavier rare earth complexes, which give the oxide directly. The oxide formation temperatures do not alter significantly in the series. The decomposition sequences can be represented as follows ... 

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