Solid mechanistic studies

NMR, IR, and HPLC have become the tools of choice for such mechanistic studies [128,132,143-159]. CP-MAS based on - C-NMR has been useful in studying the condensations in solid PF [143]. 

Reference has already been made to the dehydration of alums (Sect. 1.2 and Table 10), decomposition of ammonium metal phosphates (Sect. 4.1.5) and the use of KMn04—KCIO4 solid solutions in mechanistic studies of the decomposition of potassium permanganate (Sect. 3.6). 

The exceptionally large ionic conductivities characteristic of certain double iodides [1182] make them particularly attractive systems for kinetic and mechanistic studies of solid—solid interaction. Countercurrent migration of Ag+ and Hg2+ in the product phase has been identified as the rate-controlling process for [1209]... 

Mechanistic Study of Thermal Solid-State Reactions... 

Since solid-state reactions can easily be monitored by continuous measurement of spectra, it is easy to study the mechanism of the reactions. For this purpose, IR spectroscopy is the most useful, because IR spectra can be measured simply as Nujol mulls or directly for any mixture of solid-solid, solid-liquid, or liquid-liquid by using the ATP (attenuated total reflection) method. Some such examples of the mechanistic study are described. 

Subsequently, a mechanistic study demonstrated that protein solubilization in the organic phase occurred simultaneously with the adsorption of w/o-MEs by the solid phase [58]. Moreover, the results of this study supported the following proposed mechanism for SPE ... 

P Singh, S Desai, D Flanagan, A Simonelli, W Higuchi. Mechanistic study of the influence of micelle solubilization and hydrodynamic factors on the dissolution rate of solid drugs. J Pharm Sci 57 959, 1968. 

Choi YM, Compson C, Lin MC, and Liu M. A mechanistic study of H2S decomposition on Ni- and Cu-based anode surfaces in a solid oxide fuel cell. Chem Phys Lett 2006 421 179-183. 

The tri-t-butylnitrosobenzene, TNB, is monomeric even in the solid state, but the principal advantage of this scavenger, exemplified in the mechanistic studies described in Section 3 (p. 47), is that it functions as an ambident spin trap (Terabe and Konaka, 1973). Thus, primary alkyl radicals add to form nitroxides in the normal way, but with t-alkyl radicals, addition occurs at oxygen, alkoxyaminyl radicals (ArNOR) being formed. Secondary alkyl radicals give mixtures of both species (Fig. 5). The alkoxyaminyl radicals have a lower g-value than the nitroxides (ca. 2.004 vs. 2.006) and their spectra are therefore centred at slightly higher field positions than those of the nitroxides. 

A mechanistic study by Haynes et al. demonstrated that the same basic reaction cycle operates for rhodium-catalysed methanol carbonylation in both homogeneous and supported systems [59]. The catalytically active complex [Rh(CO)2l2] was supported on an ion exchange resin based on poly(4-vinylpyridine-co-styrene-co-divinylbenzene) in which the pendant pyridyl groups had been quaternised by reaction with Mel. Heterogenisation of the Rh(I) complex was achieved by reaction of the quaternised polymer with the dimer, [Rh(CO)2l]2 (Scheme 11). Infrared spectroscopy revealed i (CO) bands for the supported [Rh(CO)2l2] anions at frequencies very similar to those observed in solution spectra. The structure of the supported complex was confirmed by EXAFS measurements, which revealed a square planar geometry comparable to that found in solution and the solid state. The first X-ray crystal structures of salts of [Rh(CO)2l2]" were also reported in this study. 

Rebek J. Mechanistic studies using solid supports—the 3-phase test. Tetrahedron 1979 35 723-731. 

These complexes are effective catalysts in epoxidation reactions with H2O2 and alkyl hydroperoxides. Several detailed mechanistic studies have been carried out in particular, it has been shown that, when the alkyl chain contains a double bond, no autoepoxidation is observed both in the solid state and in solution. Nevertheless, if f-BuOOH is added, the epoxidation of the olefinic moiety immediately takes place. Therefore, it has been suggested that these complexes are not the active species in the oxygen transfer step to the substrate, but they behave as catalysts for the primary peroxidic oxidant. On the basis of kinetic, spectroscopic and theoretical studies, the authors provided a mechanism, whose key steps are sketched in Scheme 12. In this context a major role appears to be played by the fluxionality of the particular ligands used . ... 

Fig. 5. Observed hearing threshold shift (dB) at 1, 2 and 4 kHz versus measured unbound (upper panel) and total plasma quinine concentration in a subject who received a computer-controlled quinine infusion. The reduced sigmoid Fmax model has been applied and is shown as the solid line. Note that the y axis is hy definition a log scale. (From Karlsson KK, Beminger E, Gustafsson LL, Al-van G. Pronounced quinine-induced cochlear hearing loss. A mechanistic study in one volunteer at multiple stable plasma concentrations. J Audiol Med 1995 4 12-24, with permission.)...

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