Methylcyclohexane is a colourless liquid

Liquid

Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...

 with a faint benzene

Benzene

Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....

-like odour. Its molecular formula is C₇H₁₄. Methylcyclohexane is used in organic synthesis

Organic synthesis

Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...

 and as a solvent

Solvent

A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...

 for cellulose

Cellulose

Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

 ethers. It is a component of jet fuel

Jet fuel

Jet fuel is a type of aviation fuel designed for use in aircraft powered by gas-turbine engines. It is clear to straw-colored in appearance. The most commonly used fuels for commercial aviation are Jet A and Jet A-1 which are produced to a standardized international specification...

 and is also a component of correction fluids.

Structure

Monosubstituted methylcyclohexane has one methyl branch on one carbon of the cyclohexane

Cyclohexane

Cyclohexane is a cycloalkane with the molecular formula C6H12. Cyclohexane is used as a nonpolar solvent for the chemical industry, and also as a raw material for the industrial production of adipic acid and caprolactam, both of which being intermediates used in the production of nylon...

 ring. Like all substituted cyclohexanes, it can ring-flip rapidly between two chair conformations

Cyclohexane conformation

A cyclohexane conformation is any of several three-dimensional shapes that a cyclohexane molecule can assume while maintaining the integrity of its chemical bonds....

. However, a monosubstituted Methylcyclohexane exists almost exclusively in the equatorial position rather than axial. When the methyl group occupies the axial position, there is steric crowding (steric strain) by the axial hydrogens on the same side of the ring (known as the 1,3-diaxial interactions). There are two such interactions, with each methyl/hydrogen pair contributing approximately 7.61 kJ/mol strain. However, the equatorial conformation experiences no such interaction so it is more stable.

Disubstituted cyclohexanes

Cyclohexanes could also have more than one methyl branch. Disubstituted cyclohexane, or also known as dimethylcyclohexane has two methyl branches. Unlike the monosubstituted cyclohexane, there are several possible structures. The methyl groups could be on the same carbon, separate carbons and it doesn't necessarily have to be on the same face. The 1,3-diaxial strain interactions still apply to the disubstituted. If the methyl groups are on different faces and both in axial positions, there are diaxial interactions with the axial hydrogen groups on both faces. If they are on the same face, both methyl groups interact with the one hydrogen that is in axial position and there is also a methyl-methyl interaction with a steric energy of approximately 15.3 kJ/mol. If the methyl groups are on adjacent carbons of the cyclohexane, with one of them axial and the other equatorial, there would be a gauche interaction which adds to the total strain energy the molecule has. For the dimethylcyclohexane which has two methyl groups on one carbon (1,1-dimethylcyclohexane), one methyl group is axial and the other equatorial. It would have the same total strain energy as the monosubstituted cyclohexane with axial methyl.

Jet Fuel Surrogates

Methylcyclohexane is one of a group of fuels that have recently been used as components for jet fuel surrogate blends . Chemical analysis of Jet A finds a high cycloparaffin content; methylcyclohexane is one of the hydrocarbons used as Jet A surrogate in order to mimic this high presence of cycloparaffin and the associated chemical behaviour of the fuel.