Classification of Hydrocarbons

Let us review briefly the classifications of carbon-containing compounds, particularly those of interest in atmospheric chemistry. The carbon atom has four valence electrons and can therefore share bonds with from one to four other atoms. The nature of the carbon-carbon bonding in a hydrocarbon molecule basically governs the properties (as well as the nomenclature) of the molecule. 

In some sense the simplest hydrocarbon molecules are those in which all the carbon bonds are shared with hydrogen atoms except for a minimum number required for carbon-carbon bonds. Molecules of this type are referred to as alkanes or, equivalently, as paraffins. The general chemical formula of alkanes is C H2 +2. The first four alkanes 

Alkanes need not have a straight-chain structure. If a side carbon chain exists, the name of the longest continuous chain of carbon atoms is taken as the base name, which is then modified to include the type of group. Typical examples of substituted alkanes are (the numbering system is indicated below the carbon atoms)  

Alkanes may also be arranged in a ring structure, in which case the molecule is referred to as a cycloalkane. 

Alkanes generally react by replacement of a hydrogen atom. Once a hydrogen atom is removed from an alkane, the involved carbon atom has an unpaired electron and the molecule becomes a free radical, in this case an alkyl radical. Examples of alkyl radicals are 

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There are a total of eighteen different hydrocarbon series, of which the most common constituents of crude oil have been presented - the alkanes, cycloalkanes, and the arenes. The more recent classifications of hydrocarbons are based on a division of the hydrocarbons in three main groups alkanes, naphthanes and aromatics, along with the organic compounds containing the non-hydrocarbon atoms of sulphur, nitrogen and oxygen. 

The classification of hydrocarbons as aliphatic or aromatic took place m the 1860s when It was already apparent that there was something special about benzene toluene and their derivatives Their molecular formulas (benzene is CgHg toluene is C7Hj ) indicate that like alkenes and alkynes they are unsaturated and should undergo addition reac tions Under conditions m which bromine for example reacts rapidly with alkenes and alkynes however benzene proved to be inert Benzene does react with Bi2 m the pres ence of iron(III) bromide as a catalyst but even then addition isn t observed Substitu tion occurs instead ... 

Farley FF. 1977. Photochemical reactivity classification of hydrocarbons and other organic compounds. In EPA-600/3-77-001B. Inter Conf Photochemical Oxidant Pollut Control. Dimitriades B, ed. Research Triangle Park, NC, 713-726. 

Classification of Hydrocarbons (Review) 87 3-2 Molecular Formulas of Alkanes 88 3-3 Nomenclature of Alkanes 89... 

Hydrocarbons are classified by whether their carbon structure includes rings, multiple bonds, or branches. Classification of hydrocarbon structural families is shown here with the chemical formula. Structures are shown as Kekule (also called line-bond) and skeletal structures. 

Heum, O.R. 1996. A fluid dynamic classification of hydrocarbon entrapment. Pet. Geosci., 2 145-158. 

Some other contributions of organometallic compounds to fundamental research are (a) the detection of free alkyl radicals by the pyrolysis of lead alkyls (b) the classification of hydrocarbon acidity via organoalkali compounds (c) the study of Lewis acid-base interactions with Group III alkyls (d) the development of the concept of electron-deficient compounds by the study of metal alkyls (e) the discovery of stereospecific olefin polymerization and (f) the investigation of nucleophilic additions to unsaturated organic compounds via reactive metal alkyls. 

Classification of Hydrocarbons.- -In a systematic study of the compounds of carbon it is advisable to begin with a consideration of the compounds which contain hydrogen and carbon only. These substances, which are called hydrocarbons, occur in nature, are formed in certain industrial processes, and have important uses. It is not for these reasons, however, that the hydrocarbons are first studied. They are, perhaps, the simplest organic compounds, and a knowledge of their properties and reactions is the best preparation for the study of more complex substances. Further, most compounds can be considered as derived from the hydrocarbons by the replacement of one or more hydrogen atoms by other atoms or groups of atoms. 

Figure 20.4.1. General classification of hydrocarbons based on general structure.[Adapted, by permission, fi om...

What are the main classifications of hydrocarbons What are their generic molecular formulas ... 

Classification of hydrocarbons. (Based on table from K.W. Whitten, K.D. Gailey, R.E. Davis, General Chemistry, 4th ed., Saunders College Publishing, 1992.)... 

Hence, naphthalene, phenanthrene, pyrene, and biphenylene are alternant hydrocarbons, while azu-lene, pyracylene, and its isomers are non-alternant conjugated hydrocarbons. The idea of classification of hydrocarbons as alternant and non-alternant goes back to Coulson and Longuet-Higgins and the early days of HMO theory. An important property of alternant hydrocarbons, as opposed to non-alternant, is that for alternant systems all HMO eigenvalues come in pairs Xu while this is not the case for nonalternant systems. It is interesting to mention that this particular mathematical property of alternant... 

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