Methylcyclohexane

Methylcyclohexane
Names
IUPAC name
methylcyclohexane
Other names
Hexahydrotoluene
Cyclohexylmethane
Toluene hexahydride
Identifiers
108-87-2 YesY
ChemSpider 7674 YesY
Jmol interactive 3D Image
PubChem 7962
Properties
C7H14
Molar mass 98.19 g·mol−1
Appearance Colourless liquid
Odor faint, benzene-like[1]
Density 0.77 g/cm3
Melting point −126.3 °C (−195.3 °F; 146.8 K)
Boiling point 101 °C (214 °F; 374 K)
Insoluble in water
Vapor pressure 37 mmHg (20°C)[1]
Hazards
Main hazards severe fire hazard
NFPA 704
Flammability code 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g., gasoline) Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
3
1
0
Flash point −3 °C (27 °F; 270 K)
Explosive limits 1.2%-6.7%[1]
Lethal dose or concentration (LD, LC):
2250 mg/kg (mouse, oral)[2]
10172 ppm (mouse, 2 hr)
10,000-12,500 ppm (mouse, 2 hr)
15227 ppm (rabbit, 1 hr)[2]
US health exposure limits (NIOSH):
TWA 500 ppm (2000 mg/m3)[1]
TWA 400 ppm (1600 mg/m3)[1]
1200 ppm[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Methylcyclohexane is a simple organic hydrocarbon with a molecular formula is C7H14; it is a colourless liquid with a faint benzene-like odor. Methylcyclohexane is used as a solvent and occasionally as a reagent in organic synthesis and polymer chemistry. It is a component of jet fuel and is used in some consumer products such as correction fluids. It can be handled safely, but is considered a flammable and toxic liquid with consequences in case of human or other environmental exposure.

Structure and conformation

Methylcyclohexane is referred to as a monosubstituted cyclohexane because it has one branching via the attachment of one methyl group on one carbon of the cyclohexane ring. Like all substituted cyclohexanes, it can interconvert rapidly at ambient and higher temperatures between two chair conformers. However, the lowest free energy form of this monosubstituted methylcyclohexane occurs when the methyl group occupies an equatorial rather than an axial position. 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.

Uses

Methylcyclohexane is used as an organic solvent and occasionally as a reagent in organic synthesis, e.g. it is useful for dissolving for cellulose ethers and is used in some correction fluids. It is rumoured to be one of many compounds found in the lubricant and water-displacement product WD-40. However, this cannot be confirmed due to WD-40's formula being a classified trade secret. It is also one of a group of fuel substances used as a component in jet fuel surrogate blends, e.g., for Jet A fuel.[3][4]

Flammability and toxicity

Methylcyclohexane is volatile and very flammable, and is considered harmful to humans vis-a-vis its toxicity: it is a skin irritant, can cause drowsiness or dizziness on single exposure (via CNS toxicity), can be fatal if ingested and aspirated into the lungs; 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]

References

  1. 1 2 3 4 5 6 "NIOSH Pocket Guide to Chemical Hazards #0406". National Institute for Occupational Safety and Health (NIOSH).
  2. 1 2 "Methylcyclohexane". Immediately Dangerous to Life and Health. National Institute for Occupational Safety and Health (NIOSH).
  3. ↑ 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 , accessed 27 May 2014.
  4. ↑ 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 , accessed 27 May 2014.
  5. ↑ Chevron Phillips, 2014, "Material Safety Data Sheet: Methylcyclohexane (v. 1.5)", see , accessed 23 May 2014.
  6. ↑ CDC, 2014, "Methylcyclohexane," NIOSH Pocket Guide to Chemical Hazards, see , accessed 27 May 2014.
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