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(also saturated hydrocarbons or paraffins), a homologous series of hydrocarbons of the general formula CnH2n + 2; part of the class of acyclic compounds. The parent compound of the series is methane, CH4. Each succeeding member is distinguished in composition from the preceding member by the constant difference CH2. The names of the first four members of the series are methane, CH4; ethane, C2H6; propane, C3H8; and butane, C4H10. The names of subsequent homologues are derived from the Greek cardinal numbers—for example, C5H12, pentane; C8H18, octane; C10H22, decane; and C16H34, cetane. The names of all alkanes end in “-ane.”

The carbon atoms in the molecules of alkanes are linked by single bonds to give straight unbranched chains or (starting with butane) branched chains. This is the reason for the existence of structural isomers in the alkane series. The number of isomers increases rapidly with the number of carbon atoms: pentane has three isomers, decane has 75, and eicosane (C20H42) has 366, 319. Starting with the heptanes, optical isomers also appear. The alkanes are colorless gases through butane and neopentane, liquids from C5H12 through C17H36, and solids thereafter. The boiling points of alkanes with branched chains are somewhat lower, and the melting points higher, than those of normal isomers. All alkanes are virtually insoluble in water but are readily soluble in numerous organic liquids.

Under normal conditions, alkanes are chemically the most inert hydrocarbons (hence the name “paraffins,” from the Latin parum, “little,” and affinitas, “affinity”). However, under relatively harsh conditions their hydrogen atoms may be replaced by other atoms and groups. Many such reactions are the basis of industrial processes for the manufacture of numerous important products. Chlorination of alkanes yields methyl chloride, methylene chloride, and chloroform; nitration yields nitroparaffins. Ultraviolet irradiation of a mixture of alkanes with sulfur dioxide and chlorine yields the sulfonyl chlorides, CnH2n + 1SO2CI. Oxidative sulfonation yields the sulfonic acids, CnH2n + 1 SO2-OH, and oxidation of the lower alkanes yields alcohols, aldehydes, ketones, and acids. Oxidation of solid alkanes to produce higher fatty acids is also of great industrial importance. Catalytic dehydrogenation of alkanes yields olefins (propylene, butenes, and amylenes) and diolefins (butadiene and isoprene); isomerization yields isobutane and isopentane. Alkylation of isobutane with olefins gives isooctane and neohexane. The lower alkanes are capable of forming inclusion compounds (clathrates) with water. Liquid and solid normal alkanes readily form clathrates with urea. This reaction is used in industry for deparaffination of petroleum products. Branched alkanes yield clathrates with thiourea.

Alkanes are present in petroleum (5–60 percent), which is the principal source for them. They are also produced during processing of hard coal, oil shale, and other materials. They are contained in plants and beeswax. The mineral wax ozokerite consists almost completely of higher alkanes. Natural gas contains up to 99 percent methane by volume.

Individual alkanes are prepared in the laboratory mainly by hydrogenation of olefins or by fusion of salts of fatty acids with caustic alkalies. Alkanes are important raw materials for the production of intermediates in making plastics, synthetic elastomers and fibers, and detergents. They are significant components of rocket and motor fuels and are used as solvents.


References in periodicals archive ?
Table-1: (b) The variation of logarithm of specific retention volumes, Vg0 (ml/g), of alcohols and alkanes with temperature using poly(ABM%71-co-AN) as stationary phase.
For instance, while alkane substituted benzene for semi-volatile hydrocarbons (Figures 14 and 15) comprised almost 59 percent of the total concentration, the amount of the peaks related to the individual specific hydrocarbons from this group amounted to only 21 percent.
Using viscosity prediction models, binary mixtures viscosities of alkanes are generally predicted between the respective pure component viscosities (or in some cases, based on the value of interaction parameter, the binary mixture viscosity can be slightly higher than the respective pure component viscosities).
The chemical inertness of alkanes impedes the design of reaction-based chemical sensors.
At 225 and 280[degrees]C, there were only few alkanes in the components.
As shown in Table 3, the individual alkanes present in the highest concentrations were [C.
Alkanes of intermediate chain length (C10-C24) are often degraded rapidly, while very long chain alkanes are increasingly resistant to microbial degradation [12].
The liquid phases chosen in the present article were two non-linear alkanes, isooctane (2,2,4-trimethylpentane) and cyclohexane.
The Russian contributors discuss their research on liquid phase oxidation of alkanes in the presence of metal compounds, the reaction of ozone with aromatic compounds, ozonolysis of polybutadienes in solution, anti- adhesive coatings for food equipment, and the formation of polymers in fractal spaces.
Molecular beam scattering techniques were used to investigate the adsorption dynamics of alkanes on single wall carbon nanotubes (SWCNTs) supported on silica (I).
MoldWiz INT-I 117LAM is a proprietary blend of fatty organic acids, esters, alkanes and alkanols.