Carbon Terminology

The carbon terminology can be confusing because carbon is different from other elements in one important respect, that is its diversity. Unlike most elements, carbon has several material forms which are known as polymorphs (or allotropes). They are composed entirely of carbon but have different physical structures and, uniquely to carbon, have different names graphite, diamond, lonsdalite, fullerene, and others. 

In order to clarify the terminology, it is necessary to define what is meant by carbon and its polymorphs. When used by itself, the term carbon should only mean the element. To describe a carbon material, the term is used with a qualifier such as carbon fiber, pyrolytic carbon, vitreous carbon, and others. These carbon materials have an sp atomic structure, and are essentially graphitic in nature. 

Other materials with an sp atomic structure are, by common practice, called by the name of their allotropic form, i.e., diamond, lonsdalite, etc., and not commonly referred to as carbon materials, although, strictly speaking, they are. 

The presently accepted definition of these words, carbon, graphite, diamond, and related terms, is given in the relevant chapters. These definitions are in accordance with the guidelines established by the International Committee for Characterization and Terminology of Carbon and regularly published in the journal Carbon. 

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The carbon terminology was reviewed in Ch. 3, Sec. 1.1, and its proper use is important as confusion can easily prevail because of the many variations of graphite and carbon products. The synthetic graphite and carbon products can be divided into six major categories ... 

So without direct amination we are confined to semi-direct ami-nation (Strike s terminology). In Strike s opinion, the direct addition of an azide (N3) counts. Once on the beta carbon, that azide is as good as an amine. But can we get an azide directly onto safrole without having to go thru the bromosafrole intermediate as was discussed earlier Maybe we can ... 

Structures [VI] and [VII], respectively, are said to arise from head-to-tail or head-to-head orientations. In this terminology, the substituted carbon is defined to be the head of the molecule, and the methylene is the tail. Tail-to-tail linking is also possible. The term orienticity is also used to describe positional isomerism. 

Complications arising from other types of isomerism. Positional and geometrical isomerism, also described in Sec. 1.6, will be excluded for simplicity. In actual polymers these are not always so easily ignored. Polymerization of 1,2-disubstituted ethylenes. Since these introduce two different asymmetric carbons into the polymer backbone (second substituent Y), they have the potential to display ditacticity. Our attention to these is limited to the illustration of some terminology which is derived from carbohydrate nomenclature (structures [IX]-[XII]) ... 

CARBON - CARBONAND ARTIFICIALGRAPHITE - STRUCTURE TERMINOLOGY AND HISTORY] (Vol 4)... 

Whereas the foregoing ate the forms most commonly found in many appHcations in industry, there ate definitions that ate necessary not only for industrial purposes but also for consistency in the study of carbon science. Since 1975, the International Committee for Characterization and Terminology of Carbon has been working to estabUsh definitions and in 1982 pubHshed its 30 tentative definitions followed by periodic issues of further tentative definitions (10). 

Structure, Terminology, and History" under "Carbon (Carbon and Artificial Graphite)" ia ECT3rd ed., Vol. 4, pp. 556—560, byj. C. Long, Union Carbide Corp. 

The large number of individual hydrocarbons in the atmosphere and the many different hydrocarbon classes make ambient air monitoring a very difficult task. The ambient atmosphere contains an ubiquitous concentration of methane (CH4) at approximately 1.6 ppm worldwide (9). The concentration of all other hydrocarbons in ambient air can range from 100 times less to 10 times greater than the methane concentration for a rural versus an urban location. The terminology of the concentration of hydrocarbon compounds is potentially confusing. Hydrocarbon concentrations are referred to by two units—parts per million by volume (ppmV) and parts per million by carbon (ppmC). Thus, 1 fx of gas in 1 liter of air is 1 ppmV, so the following is true ... 

Several structural factors have been considered as possible causes of the anomeric effect. In localized valence bond terminology, it can be recognized that there will be a dipole-dipole repulsion between the polar bonds at the anomeric carbon in the equatorial conformation. This dipole-dipole interaction is reduced in the axial conformation, and this factor probably contributes to the solvent dependence of the anomeric effect. 

Substitution reactions by the ionization mechanism proceed very slowly on a-halo derivatives of ketones, aldehydes, acids, esters, nitriles, and related compounds. As discussed on p. 284, such substituents destabilize a carbocation intermediate. Substitution by the direct displacement mechanism, however, proceed especially readily in these systems. Table S.IS indicates some representative relative rate accelerations. Steric effects be responsible for part of the observed acceleration, since an sfp- caibon, such as in a carbonyl group, will provide less steric resistance to tiie incoming nucleophile than an alkyl group. The major effect is believed to be electronic. The adjacent n-LUMO of the carbonyl group can interact with the electnai density that is built up at the pentacoordinate carbon. This can be described in resonance terminology as a contribution flom an enolate-like stmeture to tiie transition state. In MO terminology,.the low-lying LUMO has a... 

In this chapter the results of detailed research on the realistic electronic structure of single-walled CNT (SWCNT) are summarised with explicit consideration of carbon-carbon bond-alternation patterns accompanied by the metal-insulator transition inherent in low-dimensional materials including CNT. Moreover, recent selective topics of electronic structures of CNT are also described. Throughout this chapter the terminology "CNT stands for SWCNT unless specially noted. 

Bromide ion forms a bond to the primary carbon by pushing off a water molecule. This step is bimolecular- because it involves both bromide and heptyloxonium ion. Step 2 is slower than the proton transfer in step 1, so it is rate-determining. Using Ingold s terminology, we classify nucleophilic substitutions that have a bimolecular- rate-determining step by the mechanistic symbol 8 2. 

Using the terminology of Sec. 5 of the Introduction we can state the number of those structurally isomeric homologues of a given basic compound which contain n carbon atoms more than the basic compound is asymptotically proportional to the number of the structurally isomeric The formula indicates, furthermore, how the... 

A terminology to identify carbons that are graphitizable or those that are none graphitizable by heat treatment has been adopted. Hard carbons are those carbons that are nongraphitizable and are mechani-... 

Now let s apply the same terminology to the groups on a chair. Each carbon atom has two groups, one pointing above the ring (up) and one pointing below the ring (down) ... 

In 1,2-eliminations involving carbon atoms (i.e. most), the atom from which Y is lost is usually designated as the l-(a-) carbon and that losing (usually) H as the 2-(/ -) carbon in the older a/J-terminology, the a- is commonly omitted, and the reactions are referred to as p-eliminations. Among the most familiar examples are base-induced elimination of hydrogen halide from alkyl halides—this almost certainly the most common elimination of all—particularly from bromides (1) ... 

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