Solid-state reactions mechanisms

It is probably true that many of the descriptions of physical and solid state reaction mechanisms now existing in the literature are only partially correct. It would appear that part of the frontier of knowledge for Chemistry of The Solid State wiU lie in measurement of physical and chemical properties of inorgcuiic compounds as a function of purity. 

Our first step will be to delineate known solid state reaction mechanisms. Mechanisms Relating to Solid State Reactions Phase changes... 

Aspartame is relatively unstable in solution, undergoing cyclisation by intramolecular self-aminolysis at pH values in excess of 2.0 [91]. This follows nucleophilic attack of the free base N-terminal amino group on the phenylalanine carboxyl group resulting in the formation of 3-methylenecarboxyl-6-benzyl-2, 5-diketopiperazine (DKP). The DKP further hydrolyses to L-aspartyl-L-phenyl-alanine and to L-phenylalanine-L-aspartate [92]. Grant and co-workers [93] have extensively investigated the solid-state stability of aspartame. At elevated temperatures, dehydration followed by loss of methanol and the resultant cyclisation to DKP were observed. The solid-state reaction mechanism was described as Prout-Tompkins kinetics (via nucleation control mechanism). 

Although the estimates of range (more than five molecular distances) and cooperativity (three or four sites), which were developed in a semiquantitative treatment of long-range stress, must be considered highly approximate, the danger for simplistic interpretation of solid-state reaction mechanisms and the power of IR spectroscopy for studying such complications were clearly demonstrated [83]. 

Wang, J.A., R. Limas-Ballesteros, T. Lopez, A. Moreno, R. Gomez, O. Novaro and X. Bokhimi (2001b). Quantitative determination of titanium lattice defects and solid-state reaction mechanism in iron-doped Ti02 photocatalysts. Journal of Physical Chemistry B, 105(40), 9692-9698. 

In this chapter, we describe the isomerization, dimerization, and topochemical polymerization of benzyl muconates with various kinds of substituents on the benzyl ester group (Scheme 24.1), in order to reveal the solid-state reaction mechanism by the direct observation of crystal structures which change during the reactions. 

We have already covered the first three in some detail. Impingement involves the point where the growing particles actually touch each other and have used up all of the nutrient which had originally caused them to start growing in the first place. This mechanism occurs in both precipitation and solid state reaction mechanisms. It is for this reason that we did not discuss precipitation until we examined solid state reaction mechanisms. 

USE OF Fe57 MOSSBAUER SPECTROSCOPY IN MONrTORING SOLID-STATE REACTION MECHANISMS... 

USE OF MOSSBAUER SPECTROSCOPY IN MONITORING SOLID-STATE REACTION MECHANISMS TOWARD IRON OXIDES... 

Topical issues on the advantages and limitations of TG-MS with respect to other evolved gas analysis techniques have recently been summarised by Raemaekers and Bart a.l0] in a review on TG-MS thermal degradation of polymers. The advantageous applications of the technique in polymer science can be extended from qualitative thermal degradation analyses to thermooxidation, structural characterisation and chemical analyses, kinetics, solid-state reaction mechanisms, chemical reactivity and curing, quantitative analyses, and finally product formulation and development. 

Considering a specified temperature Tf, which is common to both the heating rates pi and p , the solid state reaction mechanism which remains operative, can be identified by using the expression shown below. 

Amorphous networks, 4-5 nAmorphous solid synthesis via ultrathin-film multilayer composites analysis of solid-state reaction mechanisms, 357,358/ application to synthesis of metastable ternary compounds, 366 control of crystallization of amorphous aUoy, 360,363,365-367/ control of formation of homogeneous amorphous alloy, 360,361-36 differential scanning calorimetric procedure, 359-360 grazing measurement procedure, 359 lugb-angje XRD procedure, 359 length sddes vs. course of solid-state reactions, 360,361-362/363 quantitative analysis of interdiffiision reaction, 356-357... 

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