Octane is a

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic; their odor is usually fain ...

and also an

alkane In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in whi ...

with the

chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...

C₈H₁₈, and the condensed structural formula CH₃(CH₂)₆CH₃. Octane has many

structural isomer In chemistry, a structural isomer (or constitutional isomer in the IUPAC nomenclature) of a compound is a compound that contains the same number and type of atoms, but with a different connectivity (i.e. arrangement of bonds) between them. The ...

s that differ by the location of branching in the carbon chain. One of these isomers,

2,2,4-trimethylpentane 2,2,4-Trimethylpentane, also known as isooctane or iso-octane, is an organic compound with the formula (CH3)3CCH2CH(CH3)2. It is one of several isomers of octane (C8H18). This particular isomer is the standard 100 point on the octane rating scale ...

(commonly called iso-octane), is used as one of the standard values in the

octane rating An octane rating, or octane number, is a standard measure of a liquid fuel, fuel's ability to withstand Compression ratio, compression in an internal combustion engine without causing engine knocking. The higher the octane number, the more compres ...

scale. Octane is a component of

gasoline Gasoline ( North American English) or petrol ( Commonwealth English) is a petrochemical product characterized as a transparent, yellowish, and flammable liquid normally used as a fuel for spark-ignited internal combustion engines. When for ...

and petroleum. Under

standard temperature and pressure Standard temperature and pressure (STP) or standard conditions for temperature and pressure are various standard sets of conditions for experimental measurements used to allow comparisons to be made between different sets of data. The most used ...

, octane is an odorless, colorless liquid. Like other short-chained alkanes with a low molecular weight, it is volatile, flammable, and toxic. Octane is 1.2 to 2 times more toxic than

heptane Heptane or ''n''-heptane is the straight-chain alkane with the chemical formula H3C(CH2)5CH3 or C7H16. When used as a test fuel component in anti-knock test engines, a 100% heptane fuel is the zero point of the octane rating scale (the 100 poi ...

Isomers

N-octane has 23 constitutional isomers. 8 of these isomers have one

stereocenter In stereochemistry, a stereocenter of a molecule is an atom (center), axis or plane that is the focus of stereoisomerism; that is, when having at least three different groups bound to the stereocenter, interchanging any two different groups cr ...

; 3 of them have two stereocenters. Octane_stereo_isomers_10_3_4_dimethylhexane

Achiral isomers: *

2-Methylheptane 2-Methylheptane is a branched-chain alkane and an isomer of octane. It is an heptane molecule with a methyl group attached to its second atom. It is a flammable colorless liquid used as fuel. If the standard definition of the prefix "iso-" is str ...

* 4-Methylheptane * 3-Ethylhexane *

2,2-Dimethylhexane The comma is a punctuation mark that appears in several variants in different languages. Some typefaces render it as a small line, slightly curved or straight, but inclined from the vertical; others give it the appearance of a miniature fille ...

2,5-Dimethylhexane 2,5-Dimethylhexane is a branched alkane used in the aviation industry in low revolutions per minute helicopters. As an isomer of octane, the boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liq ...

* (''meso'')-3,4-Dimethylhexane *

3,3-Dimethylhexane 3,3-Dimethylhexane is a colourless, odourless liquid, chemical compound in the family of hydrocarbons which has a formula of C8H18. It is an isomer of octane, where two methylene hydrogens at the third position in a hexane molecule have been replac ...

* 3-Ethyl-2-methylpentane * 3-Ethyl-3-methylpentane *

2,2,4-Trimethylpentane 2,2,4-Trimethylpentane, also known as isooctane or iso-octane, is an organic compound with the formula (CH3)3CCH2CH(CH3)2. It is one of several isomers of octane (C8H18). This particular isomer is the standard 100 point on the octane rating scale ...

(i.e. iso-octane) * 2,3,3-Trimethylpentane * 2,3,4-Trimethylpentane * 2,2,3,3-Tetramethylbutane Chiral isomers: * (3''R'')-3-Methylheptane * (3''S'')-3-Methylheptane * (3''R'')-2,3-Dimethylhexane * (3''S'')-2,3-Dimethylhexane * (4''R'')-2,4-Dimethylhexane * (4''S'')-2,4-Dimethylhexane * (3''R'',4''R'')-3,4-Dimethylhexane * (3''S'',4''S'')-3,4-Dimethylhexane * (3''R'')-2,2,3-Trimethylpentane * (3''S'')-2,2,3-Trimethylpentane

Production and use

In petrochemistry, octanes are not typically differentiated or purified as specific compounds. Octanes are components of particular boiling fractions. A common route to such fractions is the alkylation reaction between iso-butane and 1-butene, which forms iso-octane. Octane is commonly used as a solvent in paints and adhesives.

References

External links

* * * Dr. Duke's Phytochemical and Ethnobotanical Databases, Octane

{{Hydrides by group Alkanes Hydrocarbons