Catenation, of carbon

Cyclic peralkylsilanes exhibit unique behavior which distinguishes these compounds from saturated catenates of carbon. In some ways, the properties of the cyclosilanes resemble these of poly-unsaturated or aromatic hydrocarbons. As shown in Table 12, five-membered permethyl cyclic silane shows a higher oxidation potential compared with... 

German chemist Friedrich Kekuie (1829-1896) was Professor of Chemistry at the universities of Ghent and Bonn. He proposed the concept of the carbon chain , or the catenation of carbon, as the basis of many organic compounds, in the 1860s, he turned his attention to aromatic compounds. Benzene had been identified by Faraday in 1825. it was known that the empiricai formuia of benzene was CgHs, but its structure remained a mystery untii Kekuie proposed his cyciic structure in 1865. 

On the other hand, formates are less stable. This seems to be related to the H-CO-S atomic catenation in which 2 is an oxygen or chlorine atom. Nevertheless, with esters, the presence of a base as well as a high temperature and pressure are necessary. In the presence of sodium methoxide in a small quantity (0.5%), at 100°C and under 70 bar, methyl formate decomposes according to the reaction below the violent release of carbon oxide creates a dangerous overpressure in the apparatus ... 

In both papers two key ideas were set forth — 1) the idea of the tetravalent carbon atom, and 2) the concept of catenation (that carbon atoms could form chains). Both papers also stated explicitly, for the first time, what became known as the chemical stracture of a compound, and the idea that the properties of the compoimds depended on the properties and arrangement of their component atoms, rather than the more complex (and less well defined) radicals. The appearance of these papers also resulted in a polemical interchange over priority that left Couper a broken man, and boosted Kekule (with the help of Wurtz, amongst others) to the top echelons of organic chemistry in Emope (5). 

The tendency of atoms of certain elements to form chains with themselves (homoatomic catenation) or in alternation with other atoms (heteroatomic catenation) is of extreme importance in chemistry. The immense subject of organic chemistry and, indeed, life as we know it depend on the special ability of carbon to catenate from the chemical engineering standpoint, catenation and the associated ability to form molecular rings and cages provide opportunities to make materials of desired mechanical, electrical, thermal, chemical, or catalytic properties. 

Sulfur is usually only divalent, unless oxidized, and its catenation chemistry is therefore more limited and less familiar than that of carbon. Solid a-sulfur contains very stable eight-membered crown like rings, Ss,... 

The outstanding characteristic of the chemistry of carbon is its ability to catenate. Catenation is the bonding of atoms of the same element to each other, and carbon shows this tendency to a far greater extent than any other element. Even its elemental forms are characterized by extended structural units. Graphite is the most common form of elemental carbon, but it exists in two forms, both of which are composed of layers. One form has the layers oriented as shown in Figure 10.1. 

Of all of the elements of the Periodic Table, only neighboring carbon and boron share the properties of self-bonding (catenation) and the support of electron-delocalized structures based upon these catenated frameworks. Carbon catenation, of course, leads to the immense field of organic chemistry. Boron catenation provides the nido-, arachno-, and /i p/io-boranes, which may be considered as the borane equivalents of aliphatic hydrocarbons, and the discrete families of c/oso-borane derivatives which bear a for nal resemblance to the aromatic hydrocarbons, heterocycles, and metallocenes. Aside from these analogies, boron and carbon chemistries are also important to each other through their extravagant ability to mix m ways not available to other element-pairs. Thus, the conflux of boron and carbon chemistries effectively provides an element-pair for exploitation in a variety of novel ways. 

The direct linking of like atoms, such an essential feature of carbon chemistry, occurs to only a limited extent with other elements. Metal-metal bonds are not uncommon but they are always weak examples are found in the polynuclear carbonyls (p. 306) and compounds such as SugRg and PbgRfi (R = alkyl). Among the other non-metals catenation is displayed by boron, silicon, germanium, phosphorus and sulphur none of the substances... 

It is probably fair to say that life reflects and depends on three chemical aspects (1) hybridization of carbon and oxygen (as well as nitrogen), (2) the facile way carbon atoms may bind to other carbon atoms, and (3) the unique ability of hydrogen to form H-bonds. The catenation and tetrahedral geometry of the carbon atoms are the fundamental features of all organic compounds in cells. However, the most abundant molecule in any living cell is water. 

Recall that the linking of Kke atoms is called catenation. The ability of carbon to catenate is discussed in Section 21.3. 

The particular strength of the C—C bond contributes towards the fact that catenation in carbon compounds is... 

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