Intercalation compound intermediates

The failure to find evidence for intercalation compound intermediates in steam gasification indicates the importance of sigma, rather than pi, electrons in the reaction, and is consistent with the view of the importance of the attack by gaseous molecules on the edges of graphite planes (39). 

It is believed that the discharge mechanism involves the formation of an intermediate lithium intercalation compound in which both lithium and fluorine are situated between the carbon layers of the graphitic structure. The carbon formed is graphitic and improves the cell performance as the discharge progresses, leading to a high cathode utilization - close to 100% for low currents. The lithium fluoride precipitates. 

Potassium carbonate is a well-known catalyst for the steam gasification of carbonaceous materials. We discuss the use of in situ high temperature X-ray diffraction to demonstrate that intercalation compound-like structures are not involved as stable intermediates. 

The reaction of various carbonaceous materials with steam to yield CO, CO2, and H2 has been intensively studied. Of special interest has been the catalysis of this reaction by various alkali metal containing compounds, most notably potassium carbonate (32-37). Various mechanisms have been proposed, some including alkali metal atoms (37) or even graphite intercalation compounds (38) as intermediates. 

The overall current-producing reaction (11.8) describes the process of cell discharge only approximately. The intermediate product of cathodic polyfluorocarbon reduction is assumed to be a certain solvated intercalation compound C-F-Li decomposed in the course of discharge. 

An optimal SEI layer formation not only minimizes the irreversible capacity, and thus the energy density of the cell, it also affects the cycling stability, rate capabiUty, and safety aspects of the cell. hi addition, an effective SEI layer suppresses the electrochemical exfoliation of graphite caused by the co-intercalation of solvated Uthium between the graphite layers. The unstable solvated Uthium intercalation compound formed as a short-living intermediate is decomposed... 

Intercalation of [Ru(bpy)3] " into MnPS3 (103-105) and niobate (K4Nb60i7 3H20) (106,107) has been reported as well. From spectroscopic studies of the [Ru(bpy)3] -MnPS3 system, it was concluded that intCTcalated [Ru(bpy)3] + is bound weakly. Nakato et al. have prepared two types of intercalation compounds of K4Nb60i7 with [Ru(bpy)3]. Two types of alkylammonium-intercalated K NbeO were used as intermediates. One compound involves [Ru(bpy)3] in only interlayer I, and the other involves Ru(II) in both interlayers I and II (106). Since the electronic properties of the hosts (both niobate and MnPSs) are quite different from those of smectites, one may observe unique photoprocesses. Possible surface dilution effects on the photophysics of [Ru(bpy)3] have been reported for zirconium phosphate (108) and K4Nb6Oi7(107) systems. 

None of the compounds or their in vivo intermediates is likely to bind covalently with DNA and other macromolecules. Other ways of binding with DNA, such as intercalation, cannot be ruled out. There is some membrane transport, albeit limited. It is not possible, therefore, to conclude that they are not mutagens, teratogens, or carcinogens. 

Typical OH-scavengers suppress this reaction of (OP)2Cu+ (Que et al. 1980) yet, acetate and benzoate seem to be equally efficient, despite the fact that acetate is nearly two orders of magnitude less reactive towards OH than benzoate (k=7 X 107 dm3 mol-1 s 1 vs k = 5 X 109 dm3 mol-1 s 1 Buxton et al. 1988), and obviously it is not a freely diffusing OH that is responsible for the reaction. The reaction is also suppressed by Cu-complexing compounds and by transition metal ions such as Zn2+, Co2+, Cd2+ and Ni2+ that form stable complexes with 1,10-phenanthroline (Que et al. 1980) and also by competitive intercalators such as ethidium bromide and 2,9-dimethyl-l,10-phenanthroline (Reich et al. 1981). Interestingly, compared to its parent, the latter is inactive. NADH may serve as a reductant, but 02, seems to be a salient intermediate in this cleavage reaction, because cleavage is fully suppressed in the presence of SOD (Reich et al. 1981). 

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