Graphite inclusion compounds

A modified form of the Avrami-Erofeev equation, ln[—ln(l — a)] = nln(fe/n) - - nlnr, where is a nondimen-sional coefficient and A is a generalized rate constant, has been applied by Pinakov and Logvinenko to describe the decomposition of fluorinated graphite inclusion compounds of 1,2-dichloroethane and clathrates of manganese formates with dioxane. 

Anionic polymerization of methacrolein was investigated by several authors [244-251]. Homogeneous initiators are the anion radicals of naphthalene [242,246], 2,4-dimethyl-benzophenone [247], 4-methylbenzophenone [247], 1-benzoylnaphthalene [247], benzo-phenone [247], 4-benzoylbiphenyl [247], diphenyl ketone [249], dihydronaphthalene [249], and also BuLi [250], NaCN [245], and BU3P [245]. Also heterogeneous initiators such as the radical anions of graphite [251] formed from graphite inclusion compounds are used. 

Podall and Foster reported that the reaction of toluene with olefins with KCs, a graphite inclusion compound, gave the alkylation of the side chain. A 50% conversion of toluene to 3-phenylpentane was obtained together with higher alkylbenzenes at 298 K from toluene and ethylene. At 323 K, the main product was propylbenzene (48%) together with 3-phenylpentane and a small quantity of higher alkylated products. Similarly, the reaction of isopropylbenzene with ethylene gave a 42% yield of <-amylbenzene at 473 K. 

An example for a host molecule with a layerlike structure is graphite. Various types of both organic and inorganic inclusion compounds, as well as stoichiometric and nonstoichiometric compounds, are known. 

We shall be discussing other types of inclusion compounds formed by layered graphite and Ta 2 as well as other varieties of hosts in Chapter 8, which deals with intercalation chemistry. 

The history of inclusion compounds (1,2) dates back to 1823 when Michael Faraday reported the preparation of the clathrate hydrate of chlorine. Other early observations include the preparation of graphite intercalates in 1841, the 3-hydroquinone H2S clathrate in 1849, the choleic acids in 1885, the cyclodextrin inclusion compounds in 1891, and the Hofmann s clathrate in 1897. Later milestones of the development of inclusion compounds refer to the tri-o-thymotide benzene inclusion compound in 1914, phenol clathrates in 1935, and urea adducts in 1940. 

Sir Humphry Davy discovery of chlorine hydrate 1823 - Michael Faraday formula of chlorine hydrate 1841 - C. Schafhautl study of graphite intercalates 1849 - F. Wohler /Lquinol H2S clathrate 1891 - Villiers and Hebd cyclodextrin inclusion compounds... 

In principle, the negatively charged, presumably planar network I can be combined with one molar equivalent of tetraalkylammonium ion IGN"1" of the right size as interlayer template to yield a crystalline inclusion compound of stoichiometric formula (IGN+) I C(NIG ) ICO2 that is reminiscent of the graphite intercalates. Anionic network n, on the other hand, needs twice as many monovalent cations for charge balance, and furthermore possesses honeycomb-like host cavities of diameter 700 pm that must be filled by... 

The chemistry of inclusion compounds also looks back on a lively history There are many events of significance in the area of inclusion chemistry till the middle of the twentieth century including the discovery of new inclusion compounds and hosts (Fig. 1), among them the graphite intercalates, the P-quinol and cyclodextrin inclusion compounds, the Hofmann-type clathrates as well as the inclusion compounds of tri-o-thymotide, Dianin s compound, the choleic acids, of phenols, of urea and others specified in comprehensive monographs... 

Hofmann-type clathrates Werner clathrates clathrate hydrates inclusion compounds of urea, thiourea, and selenourea cyclodextrins calixarenes gossypol hexa-hosts hydroquinone phenol and Dianin s compounds graphite intercalates natural and pillared clays and others. Such studies contributed to the birth of supramolecular chemistry, with relevance to a new understanding of the world of materials that was emphasized with a Nobel Prize. 

The concept of inclusion is as old as humankind. The hand is capable of a variable assortment of inclusions, and many analogies are appropriate. The first verified examples of inclusion compounds date from the early 1800s. It is instructive to list the dates of record for the preparation of inclusion compounds of various types the chlorine clathrate hydrate by Faraday in 1823, graphite intercalates in 1841, the /3-quinol H2S clathrate in 1849,... 

At this time, no all-inclusive rule can be given that will predict whether a given compound will intercalate or not. Most of the information available seems to have been obtained empirically. Such analogies as similar chemical properties have been helpful. The many factors that infiuence the intercalation process have been surveyed by Herold (H14). In Tables II-VI are listed metal halides considered to intercalate into graphite, together with some structural information (S2J, i 9). Several general characteristics have been ascribed to intercalat-... 

Inclusion of inorganic compounds such as graphite, quartz fiber felt, days and metal oxides is another way to modify the porosity of the sol-gel matrices... 

The structure of the intercalates are of considerable interest, in that the intercalate material enters the graphite layers to form in the final analysis, a one-to-one graphite-intercalate layer structure. Intermediate compounds involve inclusion of the material in, for example, a second, fourth, or fifth layer rather than dilution of the amount in the same layer. The chemical bonding in the compounds appears to be ionic and certainly involves electron transfer probably, for example, from potassium to the upper pi-band of graphite. ... 

Intercalation constitutes an important case of inclusion phenomena in which the host lattice is characterized by a lamellar structure [39]. Graphite yields both anion and cation intercalation compounds and charge transfer processes are the driving forces for their formation. 

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