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CAS number 591-76-4
RTECS number MO3871500
Molecular formula C7H16
Molar mass 100.20 g/mol
Appearance colorless liquid
Density 0.67 g/ml, liquid
Melting point

−118 °C (155 K)

Boiling point

90 °C (363 K)

Solubility in water Immiscible
EU classification Flammable (F)
Harmful (Xn)
Dangerous for
the environment (N)
NFPA 704
Flash point −18 °C
220 °C
Explosive limits 1.0–6.0%
Related Compounds
Related alkanes Hexane
Related compounds Methylcyclohexane
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

2-Methylhexane (C7H16, also known as isoheptane, ethylisobutylmethane) is an isomer of heptane. It is structurally a hexane molecule with a methyl group attached to its second carbon atom. It exists in most commercially available heptane merchandises as an impurity but is usually not considered as impurity in terms of reactions since it has very similar physical and chemical properties when compared to n-heptane (straight-chained heptane).

Being an alkane, 2-methylhexane is insoluble in water, but is soluble in many organic solvents, such as alcohols and ether. However, 2-methylhexane is more commonly considered as a solvent itself. Therefore, even though it is present in many commercially available heptane products, it is not considered as a destructive impurity, as heptane is usually used as a solvent. Nevertheless, by concise processes of distillation and refining, it is possible to separate 2-methylhexane from n-heptane.

Within a group of isomers, those with more branches tend to ignite more easily and combust more completely. Therefore, 2-methylhexane has a lower autoignition temperature and flash point when compared to heptane. Theoretically 2-methylhexane also burns with a less sooty flame, emitting higher-frequency radiation; however, as heptane and 2-methylhexane differ by only one carbon atom, in terms of branching, both burn with a bright yellow flame when ignited.

Compared to n-heptane, 2-methylhexane also has lower melting and boiling points. It is worth noting that most for most hydrocarbon isomers, the straight-chained isomer has a lower freezing point but a higher boiling point than the branched isomer. The case of 2-Methylhexane and heptane constitutes an exception to this rule. A lower density of liquid is found in 2-Methylhexane than heptane.

On the NFPA 704 scale, 2-methylhexane is listed as a reactivity level-0 chemical, along with various other alkanes. In fact, most alkanes are unreactive except in extreme conditions, such as combustion or strong sunlight. At the presence of oxygen and flame, 2-methylhexane, like heptane, combusts mostly completely into water and carbon dioxide. With UV-light and mixed with halogens in solvents, usually bromine in 1,1,1-trichloroethane, a substitution reaction occurs.


    1. ChemExper chemical catalog
    2. Matheson chemical safety catalog
    3. Information about Isoheptane from International Labour Association
    This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "2-Methylhexane". A list of authors is available in Wikipedia.
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