Hydrocarbons, classification cyclic

Additioneilly, "classes" or types of hydrocarbons were and still are determined based on the capability to isolate them by separation techniques. The four types usually sought eue paraffins, olefins, naphthenes, and aromatics. Paraffinic hydrocarbons include both normal and branched alkanes. Olefins refer to normal and branched alkenes that contain one or more double or triple carbon-carbon bonds. Naphthene (not to be confused with naphthalene ) is a term of the petroleum industry that refers to the saturated cyclic hydrocarbons or cycloalkanes. Finally, aromatics include all hydrocarbons containing one or more rings of the benzenoid structure. These general hydrocarbon classifications are complicated by many combinations of the above types, for example, olefinic aromatics (styrene) or alkylbenzenes (cumene). Table 4 presents a summary of the hydrocarbon types usually found in specific petroleum fractions. 

G.l.c. papers of interest include the classification of 22 acyclic monoterpenoid alcohols according to retention indexes, resolution of cyclic ketones [e.g. ( )-menthone, ( )-isomenthone] as diethyl (+)-tartrate acetals, and the use of lanthanide shift reagents to resolve non-terpenoid racemic epoxides.The occurrence and prevention of monoterpenoid hydrocarbon isomerization during silica gel chromatography has been examined and the separation of monoterpenoids and sesquiterpenoids by gel permeation chromatography is reported. Monoterpenoid hydrocarbons have been selectively extracted from essential oils using dimethylsilicone. ... 

One means of classification depends on the way in which carbon atoms are connected. Chain aliphatic hydrocarbons are compounds consisting of carbons linked either in a single chain or in a branched chain. Cyclic hydrocarbons are aliphatic compounds that have carbon atoms linked in a closed polygon (also referred to as a ring). For example, hexane (single) and 2-methylpentane (branched) are chain aliphatic molecules, while cyclohexane is a cyclic aliphatic compound. 

Another means of classification depends on the type of bonding that exists between carbons. Hydrocarbons which contain only carbon-to-carbon single bonds are called alkanes. These are also referred to as saturated molecules. Hydrocarbons containing at least one carbon-to-carbon double bond are called alkenes, and those compounds with at least one carbon-to-carbon triple bond are called alkynes. These are compounds that are referred to as unsaturated molecules. Finally, a class of cyclic hydrocarbons that contain a closed loop (sextet) of electrons are called aromatic (see Chapter 14 in your text for further details). Table 28.1 distinguishes between the families of hydrocarbons. 

Benzene.—By far the most important and most numerous of these carbo-cyclic compounds have as their mother substance the hydrocarbon benzene, and the names Benzene Series, Benzene Compounds, or Benzene Derivatives are commonly used as synonymous with carbo-cyclic compounds. This has led to the usual classification of organic... 

This is a simplified classification because many hydrocarbons can be combinations of these classes, e.g. alkyl-substituted cyclic or mixed polycyclics containing both aromatic and fully saturated rings examples are shown in Fig. 1.1... 

According to Hiickel s rule, annulenes with 4n tt electrons are not aromatic. Cyclobutadiene and cyclooctatetraene are [4n]-annulenes, and their properties are more in accord with their classification as cyclic polyenes than as aromatic hydrocarbons. Among higher [4n]-annulenes, [16]-annulene has been prepared. [16]-Annulene is not planar and shows a pattern of alternating short (average 134 pm) and long (average 146 pm) bonds typical of a nonaromatic cyclic polyene. 

The chemical classification of petroleum that distinguishes between oils of a paraffin base from those of an asphaltene base was introduced into petroleum chemistry to distinguish the oils that separate paraffin on cooling from those that separate asphaltenes. The presence of paraffins is usually reflected in the paraffinic nature of the constituent fractions whereas a high asphaltic content corresponds with the naphthenic properties of the fractions. This could lead to the misconception that paraffin-base petroleum consists mainly of paraffins and that asphalt-base petroleum consists mainly of cyclic (or naphthenic) hydrocarbons. In order to avoid confusion, a mixed base has been introduced for those oils that leave a mixture of asphaltic petroleum and paraffins as residue from nondestruc-... 

Classification Sat. cyclic aliphatic ether Empiricai C4H8O Formuia CH2CH2CH2CH2O Properties Water-wh. volatile liq. ethereal odor very sol. in water sol. in alcohols, ketones, esters, ethers, hydrocarbons, oxygenated soivs. m.w. 

Inert substances insoluble in classification solvents. Hydrocarbons (the majority of cyclic and all saturated acyclic ones) (5, 22, 26) and their halogenated derivatives, diaryl ethers and their halogenated derivatives... 

With so many compounds, it is only to be expected that one would like to classify them into groups, groups into subgroups, and subgroups into still smaller classes, if necessary. Several criteria for classifications of compounds continue to be considered in chemistry, such as cyclic acyclic, organic inorganic, hydrocarbons heteroatomic systems,... 

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