- Source: Methylcyclohexane
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. A special use is in PF-1 priming fluid in cruise missiles 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 of arenes with hydroiodic acid in 1876 as part of his doctoral dissertation, Felix Wreden 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 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
Methylcyclohexane, as a component of a mixture, is usually dehydrogenated to toluene, which increases the octane rating of gasoline.
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, with properties similar to related saturated hydrocarbons such as heptane. 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". Note, while methylcyclohexane is a substructure of 4-methylcyclohexanemethanol (MCHM), it is distinct in its physical, chemical, and biological (ecologic, metabolic, and toxicologic) properties.