Methylcyclohexane (cyclohexylmethane) is an

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

with the molecular formula is CH₃C₆H₁₁. Classified as

saturated hydrocarbon 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 ...

, it is a colourless

liquid Liquid is a state of matter with a definite volume but no fixed shape. Liquids adapt to the shape of their container and are nearly incompressible, maintaining their volume even under pressure. The density of a liquid is usually close to th ...

with a faint odor. Methylcyclohexane is used as a

solvent A solvent (from the Latin language, Latin ''wikt:solvo#Latin, solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a Solution (chemistry), solution. A solvent is usually a liquid but can also be a solid, a gas ...

. It is mainly converted in naphtha reformers to

toluene Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon with the chemical formula , often abbreviated as , where Ph stands for the phenyl group. It is a colorless, water Water is an inorganic compound with the c ...

.M. Larry Campbell. "Cyclohexane" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2012. A special use is in PF-1 priming fluid in

cruise missiles A cruise missile is an unmanned self-propelled guided missile that sustains flight through aerodynamic lift for most of its flight path. Cruise missiles are designed to deliver a large payload over long distances with high precision. Modern cru ...

to aid engine start-up when they run on special nonvolatile jet fuel like JP-10. Methylcyclohexane is also used in some correction fluids (such as White-Out) as a solvent.

History

While researching

hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to redox, reduce or Saturated ...

of arenes with

hydroiodic acid Hydroiodic acid (or hydriodic acid) is a colorless liquid. It is an aqueous solution of hydrogen iodide with the chemical formula . It is a strong acid, in which hydrogen iodide is ionized completely in an aqueous solution. Concentrated aqueous ...

in 1876 as part of his doctoral dissertation, first prepared the hydrocarbon from toluene. He determined its boiling point to be 97°C, its density at 20°C to by 0.76 g/cc and named it hexahydrotoluene. It was soon identified in oil from

Baku Baku (, ; ) is the Capital city, capital and List of cities in Azerbaijan, largest city of Azerbaijan, as well as the largest city on the Caspian Sea and in the Caucasus region. Baku is below sea level, which makes it the List of capital ci ...

and obtained by other synthetic methods.

Production and use

Most methylcyclohexane is extracted from petroleum but it can be also produced by catalytic hydrogenation of toluene: :CH₃C₆H₅ + 3 H₂ → CH₃C₆H₁₁ The hydrocarbon is a minor component of automobile fuel, with its share in US

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 ...

varying between 0.3 and 1.7% in early 1990s and 0.1 to 1% in 2011. Its research and motor octane numbers are 75 and 71 respectively. As a component of a mixture, it is usually dehydrogenated to toluene, which increases the octane rating of gasoline. : MeC6H11toPhMe

It is also one of a host of substances in jet fuel surrogate blends, e.g., for Jet A fuel.

Solvent

Methylcyclohexane is used as an

organic solvent A solvent (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for p ...

, with properties similar to related saturated hydrocarbons such as

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 ...

. It is also a solvent in many types of correction fluids.

Structure

Methylcyclohexane is a monosubstituted

cyclohexane Cyclohexane is a cycloalkane with the molecular formula . Cyclohexane is non-polar. Cyclohexane is a colourless, flammable liquid with a distinctive detergent-like odor, reminiscent of cleaning products (in which it is sometimes used). Cyclohexan ...

because it has one branching via the attachment of one

methyl group In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula (whereas normal methane has the formula ). In formulas, the group is often abbreviated a ...

on one carbon of the cyclohexane ring. Like all cyclohexanes, it can interconvert rapidly between two chair conformers. The lowest

energy Energy () is the physical quantity, quantitative physical property, property that is transferred to a physical body, body or to a physical system, recognizable in the performance of Work (thermodynamics), work and in the form of heat and l ...

form of this monosubstituted methylcyclohexane occurs when the methyl group occupies an equatorial rather than an axial position. This equilibrium is embodied in the concept of

A value 400px, The A-value for a methyl group is 1.74 as derived from the chemical equilibrium above. This means it costs of energy to have a methyl group in the axial position compared to the equatorial position. A-values are numerical values used i ...

. In the axial position, the methyl group experiences steric crowding (steric strain) because of the presence of axial hydrogen atoms on the same side of the ring (known as the 1,3-diaxial interactions). There are two such interactions, with each pairwise methyl/hydrogen combination contributing approximately 7.61 kJ/mol of strain energy. The equatorial conformation experiences no such interaction, and so it is the energetically favored conformation.

Flammability and toxicity

Methylcyclohexane is flammable. Furthermore, it is considered "very toxic to aquatic life". Note, while methylcyclohexane is a substructure of

4-methylcyclohexanemethanol 4-Methylcyclohexanemethanol (MCHM, systematic name 4-methylcyclohexylmethanol) is an organic compound with the formula CH3C6H10CH2OH. Classified as a saturated higher alicyclic primary Alcohol (chemistry), alcohol. Both Cis–trans isomerism, c ...

(MCHM), it is distinct in its physical, chemical, and biological (ecologic, metabolic, and toxicologic) properties.CDC, 2014, "Methylcyclohexane," NIOSH Pocket Guide to Chemical Hazards, se

accessed 27 May 2014.

References

{{Authority control Hydrocarbons Hydrocarbon solvents Cyclohexyl compounds Methyl compounds