Methylcyclohexane

Last updated
Methylcyclohexane
Methylcyclohexane-2D-skeletal.png
Methylcyclohexane-3D-balls.png
Names
Preferred IUPAC name
Methylcyclohexane
Other names
Hexahydrotoluene
Cyclohexylmethane
Toluene hexahydride
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.003.296 OOjs UI icon edit-ltr-progressive.svg
PubChem CID
UNII
  • InChI=1S/C7H14/c1-7-5-3-2-4-6-7/h7H,2-6H2,1H3 Yes check.svgY
    Key: UAEPNZWRGJTJPN-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C7H14/c1-7-5-3-2-4-6-7/h7H,2-6H2,1H3
    Key: UAEPNZWRGJTJPN-UHFFFAOYAG
  • CC1CCCCC1
Properties
C7H14
Molar mass 98.189 g·mol−1
AppearanceColourless 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)
0.014 g/L at 25 °C [2]
Vapor pressure 37 mmHg (20°C) [1]

49.3 hPa at 20.0 °C
110.9 hPa at 37.7 °C [2]

-78.91·10−6 cm3/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
severe fire hazard
GHS labelling:
GHS-pictogram-flamme.svg GHS-pictogram-exclam.svg GHS-pictogram-silhouette.svg GHS-pictogram-pollu.svg
Danger
H225, H302, H304, H315, H336, H410 [2]
P210, P235, P301+P310, P331, P370+P378, P403 [2]
NFPA 704 (fire diamond)
NFPA 704.svgHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 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. gasolineInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1
3
0
Flash point −4 °C (25 °F; 269 K) [2] Closed cup
283 °C (541 °F; 556 K) [2]
Explosive limits 1.2%-6.7% [1] [2]
Lethal dose or concentration (LD, LC):
2250 mg/kg (mouse, oral) [3]
10172 ppm (mouse, 2 hr)
10,000-12,500 ppm (mouse, 2 hr)
15227 ppm (rabbit, 1 hr) [3]
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 500 ppm (2000 mg/m3) [1]
REL (Recommended)
TWA 400 ppm (1600 mg/m3) [1]
IDLH (Immediate danger)
1200 ppm [1]
Safety data sheet (SDS) [2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

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.

Contents

Methylcyclohexane is used as a solvent. It is mainly converted in naphtha reformers to toluene. [4] 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. [5] 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 [6] as part of his doctoral dissertation, [7] Felix Wreden  [ ru ] 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. [8] It was soon identified in oil from Baku and obtained by other synthetic methods. [9]

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 varying between 0.3 and 1.7% in early 1990s [10] and 0.1 to 1% in 2011. [11] Its research and motor octane numbers are 75 and 71 respectively. [12]

As a component of a mixture, it is usually dehydrogenated to toluene, which increases the octane rating of gasoline. [4]

The conversion of methylcyclohexane to toluene is a classic aromatization reaction. This platinum (Pt)-catalyzed process is practiced on scale in the production of gasoline from petroleum. MeC6H11toPhMe.png
The conversion of methylcyclohexane to toluene is a classic aromatization reaction. This platinum (Pt)-catalyzed process is practiced on scale in the production of gasoline from petroleum.

It is also one of a host of substances in jet fuel surrogate blends, e.g., for Jet A fuel. [14] [15]

Solvent

Methylcyclohexane is used as an organic solvent, with properties similar to related saturated hydrocarbons such as heptane. [16] 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". [17] Note, while methylcyclohexane is a substructure of 4-methylcyclohexanemethanol (MCHM), it is distinct in its physical, chemical, and biological (ecologic, metabolic, and toxicologic) properties. [18]

Related Research Articles

<span class="mw-page-title-main">Gasoline</span> Liquid fuel derived from petroleum

Gasoline or petrol is a petrochemical product characterized as a transparent, yellowish, and flammable liquid normally used as a fuel for spark-ignited internal combustion engines. When formulated as a fuel for engines, gasoline is chemically composed of organic compounds derived from the fractional distillation of petroleum and later chemically enhanced with gasoline additives. It is a high-volume profitable product produced in crude oil refineries.

<span class="mw-page-title-main">Toluene</span> Chemical compound

Toluene, also known as toluol, is a substituted aromatic hydrocarbon with the chemical formula C6H5CH3, often abbreviated as PhCH3, where Ph stands for the phenyl group. It is a colorless, water-insoluble liquid with the odor associated with paint thinners. It is a mono-substituted benzene derivative, consisting of a methyl group (CH3) attached to a phenyl group by a single bond. As such, its systematic IUPAC name is methylbenzene. Toluene is predominantly used as an industrial feedstock and a solvent.

<span class="mw-page-title-main">Hexane</span> Chemical compound

Hexane or n-hexane is an organic compound, a straight-chain alkane with six carbon atoms and the molecular formula C6H14.

Naphtha is a flammable liquid hydrocarbon mixture. Generally, it is a fraction of crude oil, but it can also be produced from natural-gas condensates, petroleum distillates, and the fractional distillation of coal tar and peat. In some industries and regions, the name naphtha refers to crude oil or refined petroleum products such as kerosene or diesel fuel.

Cyclohexane is a cycloalkane with the molecular formula C6H12. Cyclohexane is non-polar. Cyclohexane is a colourless, flammable liquid with a distinctive detergent-like odor, reminiscent of cleaning products. Cyclohexane is mainly used for the industrial production of adipic acid and caprolactam, which are precursors to nylon.

Methyl <i>tert</i>-butyl ether Chemical compound

Methyl tert-butyl ether (MTBE), also known as tert-butyl methyl ether, is an organic compound with a structural formula (CH3)3COCH3. MTBE is a volatile, flammable, and colorless liquid that is sparingly soluble in water. Primarily used as a fuel additive, MTBE is blended into gasoline to increase its octane rating and knock resistance, and reduce unwanted emissions.

Natural-gas condensate, also called natural gas liquids, is a low-density mixture of hydrocarbon liquids that are present as gaseous components in the raw natural gas produced from many natural gas fields. Some gas species within the raw natural gas will condense to a liquid state if the temperature is reduced to below the hydrocarbon dew point temperature at a set pressure.

<span class="mw-page-title-main">Liquid fuel</span> Liquids that can be used to create energy

Liquid fuels are combustible or energy-generating molecules that can be harnessed to create mechanical energy, usually producing kinetic energy; they also must take the shape of their container. It is the fumes of liquid fuels that are flammable instead of the fluid. Most liquid fuels in widespread use are derived from fossil fuels; however, there are several types, such as hydrogen fuel, ethanol, and biodiesel, which are also categorized as a liquid fuel. Many liquid fuels play a primary role in transportation and the economy.

Cyclopentane (also called C pentane) is a highly flammable alicyclic hydrocarbon with chemical formula C5H10 and CAS number 287-92-3, consisting of a ring of five carbon atoms each bonded with two hydrogen atoms above and below the plane. It is a colorless liquid with a petrol-like odor. Its freezing point is −94 °C and its boiling point is 49 °C. Cyclopentane is in the class of cycloalkanes, being alkanes that have one or more carbon rings. It is formed by cracking cyclohexane in the presence of alumina at a high temperature and pressure.

<span class="mw-page-title-main">Cyclohexane conformation</span> Structures of cyclohexane

Cyclohexane conformations are any of several three-dimensional shapes adopted by cyclohexane. Because many compounds feature structurally similar six-membered rings, the structure and dynamics of cyclohexane are important prototypes of a wide range of compounds.

<span class="mw-page-title-main">Catalytic reforming</span> Chemical process used in oil refining

Catalytic reforming is a chemical process used to convert naphthas from crude oil into liquid products called reformates, which are premium "blending stocks" for high-octane gasoline. The process converts low-octane linear hydrocarbons (paraffins) into branched alkanes (isoparaffins) and cyclic naphthenes, which are then partially dehydrogenated to produce high-octane aromatic hydrocarbons. The dehydrogenation also produces significant amounts of byproduct hydrogen gas, which is fed into other refinery processes such as hydrocracking. A side reaction is hydrogenolysis, which produces light hydrocarbons of lower value, such as methane, ethane, propane and butanes.

<span class="mw-page-title-main">Decalin</span> Chemical compound

Decalin, a bicyclic organic compound, is an industrial solvent. A colorless liquid with an aromatic odor, it is used as a solvent for many resins or fuel additives.

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1,2,4-Trimethylbenzene, also known as pseudocumene, is an organic compound with the chemical formula C6H3(CH3)3. Classified as an aromatic hydrocarbon, it is a flammable colorless liquid with a strong odor. It is nearly insoluble in water but soluble in organic solvents. It occurs naturally in coal tar and petroleum (about 3%). It is one of the three isomers of trimethylbenzene.

An antiknock agent is a gasoline additive used to reduce engine knocking and increase the fuel's octane rating by raising the temperature and pressure at which auto-ignition occurs. The mixture known as gasoline or petrol, when used in high compression internal combustion engines, has a tendency to knock and/or to ignite early before the correctly timed spark occurs.

3-Methylpentane is a branched alkane with the molecular formula C6H14. It is a structural isomer of hexane composed of a methyl group bonded to the third carbon atom in a pentane chain. It is of similar structure to the isomeric 2-methylpentane, which has the methyl group located on the second carbon of the pentane chain.

<span class="mw-page-title-main">Butane</span> Flammable organic compound widely used as a fuel

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Petroleum naphtha is an intermediate hydrocarbon liquid stream derived from the refining of crude oil with CAS-no 64742-48-9. It is most usually desulfurized and then catalytically reformed, which rearranges or restructures the hydrocarbon molecules in the naphtha as well as breaking some of the molecules into smaller molecules to produce a high-octane component of gasoline.

Fuel surrogates are mixtures of one or more simple fuels that are designed to emulate either the physical properties or combustion properties of a more complex fuel. While surrogate mixtures can demonstrate more than one characteristic of the desired fuel, more often than not different components are required in order to emulate the wide variety of properties that are of interest to researchers. Jet fuel is an example of a fuel requiring a surrogate for experimental research and numerical modelling due to its complexity and high content variability from one batch to the next. Neat hydrocarbon jet fuel surrogate components include decane, dodecane, methylcyclohexane, and toluene. Gasoline surrogate components include n-heptane and iso-octane. Hexadecane is a diesel surrogate component. Biodiesel surrogate components include methyl butyrate and methyl decanoate.

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 3 4 5 6 7 8 Sigma-Aldrich Co., Methylcyclohexane. Retrieved on 2022-03-17.
  3. 1 2 "Methylcyclohexane". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
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