Potassium in graphite

Interlaminar compounds of sodium or potassium in graphite will ionically polymerise styrene (and other monomers) smoothly. The occasional explosions experienced were probably due to rapid collapse of the layer structure and release of very finely divided metal. 

Potassium in graphite. Potassium can be intercalated in graphite (Fisher Scientific) very easily by heating a mixture of the two elements, in the absence of air, at 70°. The stoichiometry can be adjusted to give C8K, C24K, CWK, and C gK. 

The ionic polymerisation of styrene is as dangerous. Interlaminar compounds of sodium or potassium with graphite catalyse the polymerisation of styrene. This method can usually be controlled. Nevertheless, it gives rise to detonations. It was assumed that in these cases the lamellar structure of graphite is destroyed and the metallic particles dispersed. 

Cheng H, Pez GP, Kern G, Kresse G, Hafner J (2001) Hydrogen adsorption in potassium-intercalated graphite of second stage an ab initio molecular dynamics study. J. Phys. Chem. B. 

The presence of the potassium atoms causes the distance between the layers of carbon atoms to increase from the value of 235 pm in graphite to 540 pm in C8K. When rubidium and cesium atoms are placed between the layers, the distances between the carbon layers are 561 and 595 pm, respectively. As would be expected for materials that contain atoms of an alkali metal, these materials are extremely reactive in air, and they react explosively with water. A large number of other intercalation compounds have been prepared that have halogens, interhalogens, or metal halides as the included substances. 

Reduction of ketones. Saturated and conjugated ketones can be reduced by the reagent to alcohols, probably by a mechanism similar to electrochemical reduction (as illustrated for acetophenone in scheme I). In some cases, ptnacols are formed as well. Thus acetophenone is reduced to the alcohol (45 % yield) and the pinacol (45% yield). Generally the alcohol is the predominant product. For example, benzophenonc is reduced to benzhydrol in 98 % yield. a,)3-Unsaturated ketones are reduced to saturated alcohols. Reduction of camphor gives predominantly the exo-alcohol note that reduction with sodium in alcohol or with potassium, in the presence of graphite (not intercalated), gives predominantly the endo-alcohol. 

The universally accepted tests for superconductivity, namely a transition to zero resistance and a Meissner effect showing the expulsion of magnetic field, demonstrate unequivocally the existence of superconductivity in K Cso. The 18-K transition temperature is the highest yet reported for a molecular superconductor. This may be compared with the previously reported occurrence of superconductivity at 0.55 K in potassium-intercalated graphite. We expect that optimization of composition and crystallinity will lead to further improvement in the superconducting properties. ... 

Fig. 16.4 Staging in graphite intercalation compounds. C K. Addition of potassium proceeds through n - 4.3, 2,... to the limit in stage I C 2ffK C K. [From Whiiiinghnm. M. S. Dines, M. B. Surv. Prop. Chem. 1980. 9, SS. Reproduced with permission. ...

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