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Title: 2-methylhexane  
Author: World Heritage Encyclopedia
Language: English
Subject: Octane rating
Publisher: World Heritage Encyclopedia



CAS number 591-76-4 YesY
PubChem 11582 YesY
ChemSpider 11094 YesY
EC number 209-730-6
UN number 3295
RTECS number MO3871500
Beilstein Reference 1696856
Jmol-3D images Image 1
Molecular formula C7H16
Molar mass 100.20 g mol−1
Appearance Colorless liquid
Odor Odorless
Density 679 mg ml–1
Melting point

-119--118 °C, 154.1-155.3 K, -182--180 °F

Boiling point

90-91 °C, 362.7-363.7 K, 193-195 °F

Vapor pressure 15.7 kPa (at 37.7 °C)
kH 19 nmol Pa−1 kg−1
Refractive index (nD) 1.384
Std enthalpy of
−231.1–−228.5 kJ mol−1
Std enthalpy of
−4.8127–−4.8103 MJ mol−1
Standard molar
323.34 J K−1 mol−1
Specific heat capacity, C 222.92 J K−1 mol−1
GHS pictograms
GHS signal word DANGER
GHS hazard statements H225, H304, H315, H336, H410
GHS precautionary statements P210, P261, P273, P301+310, P331
EU Index 601-008-00-2
EU classification N
R-phrases R11, R38, R50/53, R65, R67
S-phrases (S2), S16, S29, S33
NFPA 704
Flash point −1 °C
280 °C
Explosive limits 1–7%
Related compounds
Related alkanes
Related compounds
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox 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. 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.

See also


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