Methylcyclohexane Explained

Methylcyclohexane (cyclohexylmethane) is an organic compound with the molecular formula is CH₃C₆H₁₁. Classified as saturated hydrocarbon, it is a colourless liquid with a faint odor. Methylcyclohexane is used as a solvent. It is mainly converted in naphtha reformers to toluene.^[1] Methylcyclohexane is also used in some correction fluids (such as White-Out) as a solvent.

Production and use

It can be also produced by hydrogenation of toluene:

CH₃C₆H₅ + 3 H₂ → CH₃C₆H₁₁

Methylcyclohexane, as a component of a mixture, is usually dehydrogenated to toluene, which increases the octane rating of gasoline.^[1]

It is also one of a host of substances in jet fuel surrogate blends, e.g., for Jet A fuel.^{[2] [3]}

Solvent

Methylcyclohexane is used as an organic solvent, with properties similar to related saturated hydrocarbons such as heptane.^[4] It is also a solvent in many types of correction fluids.

Structure

Methylcyclohexane is a monosubstituted cyclohexane because it has one branching via the attachment of one methyl group on one carbon of the cyclohexane ring. Like all cyclohexanes, it can interconvert rapidly between two chair conformers. The lowest energy 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. 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".^[5] Note, while methylcyclohexane is a substructure of 4-methylcyclohexanemethanol (MCHM), it is distinct in its physical, chemical, and biological (ecologic, metabolic, and toxicologic) properties.^[6]

Notes and References

1. M. Larry Campbell. "Cyclohexane" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2012.
2. Tim Edwards, Meredith Colket, Nick Cernansky, Fred Dryer, Fokion Egolfopoulos, Dan Friend, Ed Law, Dave Lenhert, Peter Lindstedt, Heinz Pitsch, Adel Sarofim, Kal Seshadri, Mitch Smooke, Wing Tsang & Skip Williams, 2007, AIAA2007-770: Development of an Experimental Database and Kinetic Models for Surrogate Jet Fuels, 45th AIAA Aerospace Sciences Meeting and Exhibit, 8-11 January 2007, Reno, Nevada, DOI 10.2514/6.2007-770, see http://arc.aiaa.org/doi/abs/10.2514/6.2007-770, accessed 27 May 2014.
3. Meredith Colket, Tim Edwards, Fred Dryer, Skip Williams, Nicholas Cernansky, David Miller, Fokion Egolfopoulos, Frederick Dryer & Josette Bellan, 2008, AIAA 2008-972: Identification of Target Validation Data for Development of Surrogate Jet Fuels, 46th AIAA Aerospace Sciences Meeting and Exhibit, 8-11 January 2007, Reno, Nevada, DOI 10.2514/6.2008-972, see http://arc.aiaa.org/doi/abs/10.2514/6.2008-972, accessed 27 May 2014.
4. D. Bryce-Smith and E. T. Blues "Unsolvated n-Butylmagnesium Chloride" Org. Synth. 1967, 47, 113.
5. Chevron Phillips, 2014, "Material Safety Data Sheet: Methylcyclohexane (v. 1.5)", see http://www.cpchem.com/msds/100000014163_SDS_EU_EN.PDF, accessed 23 May 2014.
6. CDC, 2014, "Methylcyclohexane," NIOSH Pocket Guide to Chemical Hazards, see https://www.cdc.gov/niosh/npg/npgd0406.html, accessed 27 May 2014.