Cyclohexane

Last updated
Cyclohexane
Cyclohexane Cyclohexane-2D-skeletal.svg
Cyclohexane
3D structure of a cyclohexane molecule Cyclohexane molecule chair spacefill.png
3D structure of a cyclohexane molecule
Skeletal formula of cyclohexane in its chair conformation Chair conformation of cyclohexane.svg
Skeletal formula of cyclohexane in its chair conformation
Ball-and-stick model of cyclohexane in its chair conformation Cyclohexane-chair-3D-balls.png
Ball-and-stick model of cyclohexane in its chair conformation
Names
Preferred IUPAC name
Cyclohexane [1]
Other names
Hexanaphthene (archaic) [2]
Identifiers
3D model (JSmol)
3DMet
1900225
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.003.461 OOjs UI icon edit-ltr-progressive.svg
1662
KEGG
PubChem CID
RTECS number
  • GU6300000
UNII
UN number 1145
  • InChI=1S/C6H12/c1-2-4-6-5-3-1/h1-6H2 Yes check.svgY
    Key: XDTMQSROBMDMFD-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C6H12/c1-2-4-6-5-3-1/h1-6H2
    Key: XDTMQSROBMDMFD-UHFFFAOYAZ
  • C1CCCCC1
Properties
C6H12
Molar mass 84.162 g·mol−1
AppearanceColourless liquid
Odor Sweet, gasoline-like
Density 0.7739 g/ml (liquid); 0.996 g/ml (solid)
Melting point 6.47 °C (43.65 °F; 279.62 K)
Boiling point 80.74 °C (177.33 °F; 353.89 K)
Immiscible
Solubility Soluble in ether, alcohol, acetone
Vapor pressure 78 mmHg (20 °C) [3]
−68.13·10−6 cm3/mol
1.42662
Viscosity 1.02 cP at 17 °C
Hazards
GHS labelling:
GHS-pictogram-flamme.svg GHS-pictogram-silhouette.svg GHS-pictogram-exclam.svg GHS-pictogram-pollu.svg
Danger
H225, H304, H315, H336
P210, P233, P240, P241, P242, P243, P261, P264, P271, P273, P280, P301+P310, P302+P352, P303+P361+P353, P304+P340, P312, P321, P331, P332+P313, P362, P370+P378, P391, P403+P233, P403+P235, P405, P501
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 −20 °C (−4 °F; 253 K)
245 °C (473 °F; 518 K)
Explosive limits 1.3–8% [3]
Lethal dose or concentration (LD, LC):
12705 mg/kg (rat, oral)
813 mg/kg (mouse, oral) [4]
17,142 ppm (mouse, 2  h)
26,600 ppm (rabbit, 1 h) [4]
NIOSH (US health exposure limits):
PEL (Permissible)
TWA 300 ppm (1050 mg/m3) [3]
REL (Recommended)
TWA 300 ppm (1050 mg/m3) [3]
IDLH (Immediate danger)
1300 ppm [3]
Thermochemistry
−156 kJ/mol
−3920 kJ/mol
Related compounds
Related cycloalkanes
Cyclopentane
Cycloheptane
Related compounds
 Cyclohexene
Benzene
Supplementary data page
Cyclohexane (data page)
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 ?)

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 (in which it is sometimes used). Cyclohexane is mainly used for the industrial production of adipic acid and caprolactam, which are precursors to nylon. [5]

Contents

Cyclohexyl (C6H11) is the alkyl substituent of cyclohexane and is abbreviated Cy. [6]

Production

Cyclohexane is one of components of naphtha, from which it can be extracted by advanced distillation methods. Distillation is usually combined with isomerization of methylcyclopentane, a similar component extracted from naphtha by similar methods. Together, these processes cover only a minority (15-20%) of the modern industrial demand, and are complemented by synthesis. [7]

Modern industrial synthesis

On an industrial scale, cyclohexane is produced by hydrogenation of benzene in the presence of a Raney nickel catalyst.[ citation needed ] Producers of cyclohexane account for approximately 11.4% of global demand for benzene. [8] The reaction is highly exothermic, with ΔH(500 K) = -216.37 kJ/mol. Dehydrogenation commenced noticeably above 300 °C, reflecting the favorable entropy for dehydrogenation. [9]

Industrial synthesis of cyclohexane.svg

History of synthesis

Unlike benzene, cyclohexane is not found in natural resources such as coal. For this reason, early investigators synthesized their cyclohexane samples. [10]

Failure

Surprisingly, their cyclohexanes boiled higher by 10 °C than either hexahydrobenzene or hexanaphthene, but this riddle was solved in 1895 by Markovnikov, N.M. Kishner, and Nikolay Zelinsky when they reassigned "hexahydrobenzene" and "hexanaphtene" as methylcyclopentane, the result of an unexpected rearrangement reaction.

CyclohexaneBerthelot.svg

Success

In 1894, Baeyer synthesized cyclohexane starting with a ketonization of pimelic acid followed by multiple reductions:

Cyclohexane Synthesis.svg

In the same year, E. Haworth and W.H. Perkin Jr. (1860–1929) prepared it via a Wurtz reaction of 1,6-dibromohexane.

Cyclohexane Synthesis Perkin.svg

Reactions and uses

Although rather unreactive, cyclohexane undergoes autoxidation to give a mixture of cyclohexanone and cyclohexanol. The cyclohexanone–cyclohexanol mixture, called "KA oil", is a raw material for adipic acid and caprolactam, precursors to nylon. Several million kilograms of cyclohexanone and cyclohexanol are produced annually. [9]

It is used as a solvent in some brands of correction fluid. Cyclohexane is sometimes used as a non-polar organic solvent, although n-hexane is more widely used for this purpose. It is frequently used as a recrystallization solvent, as many organic compounds exhibit good solubility in hot cyclohexane and poor solubility at low temperatures.

Cyclohexane is also used for calibration of differential scanning calorimetry (DSC) instruments, because of a convenient crystal-crystal transition at −87.1 °C. [14]

Cyclohexane vapour is used in vacuum carburizing furnaces, in heat treating equipment manufacture.

Conformation

The 6-vertex edge ring does not conform to the shape of a perfect hexagon. The conformation of a flat 2D planar hexagon has considerable strain because the C-H bonds would be eclipsed. Therefore, to reduce torsional strain, cyclohexane adopts a three-dimensional structure known as the chair conformation, which rapidly interconvert at room temperature via a process known as a chair flip. During the chair flip, there are three other intermediate conformations that are encountered: the half-chair, which is the most unstable conformation, the more stable boat conformation, and the twist-boat, which is more stable than the boat but still much less stable than the chair. The chair and twist-boat are energy minima and are therefore conformers, while the half-chair and the boat are transition states and represent energy maxima. The idea that the chair conformation is the most stable structure for cyclohexane was first proposed as early as 1890 by Hermann Sachse, but only gained widespread acceptance much later. The new conformation puts the carbons at an angle of 109.5°. Half of the hydrogens are in the plane of the ring (equatorial) while the other half are perpendicular to the plane (axial). This conformation allows for the most stable structure of cyclohexane. Another conformation of cyclohexane exists, known as boat conformation, but it interconverts to the slightly more stable chair formation. If cyclohexane is mono-substituted with a large substituent, then the substituent will most likely be found attached in an equatorial position, as this is the slightly more stable conformation.

Cyclohexane has the lowest angle and torsional strain of all the cycloalkanes; as a result cyclohexane has been deemed a 0 in total ring strain.

Solid phases

Cyclohexane has two crystalline phases. The high-temperature phase I, stable between 186 K and the melting point 280 K, is a plastic crystal, which means the molecules retain some rotational degree of freedom. The low-temperature (below 186 K) phase II is ordered. Two other low-temperature (metastable) phases III and IV have been obtained by application of moderate pressures above 30 MPa, where phase IV appears exclusively in deuterated cyclohexane (application of pressure increases the values of all transition temperatures). [15]

Cyclohexane phases [15]
NoSymmetry Space group a (Å)b (Å)c (Å)ZT (K)P (MPa)
ICubicFm3m8.6141950.1
II Monoclinic C2/c11.236.448.2041150.1
III Orthorhombic Pmnn6.547.955.29223530
IVMonoclinicP12(1)/n16.507.645.51416037

Here Z is the number structure units per unit cell; the unit cell constants a, b and c were measured at the given temperature T and pressure P.

See also

Related Research Articles

<span class="mw-page-title-main">Stereoisomerism</span> When molecules have the same atoms and bond structure but differ in 3D orientation

In stereochemistry, stereoisomerism, or spatial isomerism, is a form of isomerism in which molecules have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in space. This contrasts with structural isomers, which share the same molecular formula, but the bond connections or their order differs. By definition, molecules that are stereoisomers of each other represent the same structural isomer.

<span class="mw-page-title-main">Structural formula</span> Graphic representation of a molecular structure

The structural formula of a chemical compound is a graphic representation of the molecular structure, showing how the atoms are possibly arranged in the real three-dimensional space. The chemical bonding within the molecule is also shown, either explicitly or implicitly. Unlike other chemical formula types, which have a limited number of symbols and are capable of only limited descriptive power, structural formulas provide a more complete geometric representation of the molecular structure. For example, many chemical compounds exist in different isomeric forms, which have different enantiomeric structures but the same molecular formula. There are multiple types of ways to draw these structural formulas such as: Lewis structures, condensed formulas, skeletal formulas, Newman projections, Cyclohexane conformations, Haworth projections, and Fischer projections.

<span class="mw-page-title-main">Cycloalkane</span> Saturated alicyclic hydrocarbon

In organic chemistry, the cycloalkanes are the monocyclic saturated hydrocarbons. In other words, a cycloalkane consists only of hydrogen and carbon atoms arranged in a structure containing a single ring, and all of the carbon-carbon bonds are single. The larger cycloalkanes, with more than 20 carbon atoms are typically called cycloparaffins. All cycloalkanes are isomers of alkanes.

Mesitylene or 1,3,5-trimethylbenzene is a derivative of benzene with three methyl substituents positioned symmetrically around the ring. The other two isomeric trimethylbenzenes are 1,2,4-trimethylbenzene (pseudocumene) and 1,2,3-trimethylbenzene (hemimellitene). All three compounds have the formula C6H3(CH3)3, which is commonly abbreviated C6H3Me3. Mesitylene is a colorless liquid with sweet aromatic odor. It is a component of coal tar, which is its traditional source. It is a precursor to diverse fine chemicals. The mesityl group (Mes) is a substituent with the formula C6H2Me3 and is found in various other compounds.

Cyclohexene is a hydrocarbon with the formula (CH2)4C2H2. It is an example of a cycloalkene. At room temperature, cyclohexene is a colorless liquid with a sharp odor. Among its uses, it is an intermediate in the commercial synthesis of nylon.

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

Cyclohexanol is the organic compound with the formula HOCH(CH2)5. The molecule is related to cyclohexane by replacement of one hydrogen atom by a hydroxyl group. This compound exists as a deliquescent colorless solid with a camphor-like odor, which, when very pure, melts near room temperature. Millions of tonnes are produced annually, mainly as a precursor to nylon.

<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">Rotamer</span> Different molecular structures formed only by rotation about single bonds

In chemistry, rotamers are chemical species that differ from one another primarily due to rotations about one or more single bonds. Various arrangements of atoms in a molecule that differ by rotation about single bonds can also be referred to as different conformations. Conformers/rotamers differ little in their energies, so they are almost never separable in a practical sense. Rotations about single bonds are subject to small energy barriers. When the time scale for interconversion is long enough for isolation of individual rotamers, the species are termed atropisomers. The ring-flip of substituted cyclohexanes constitutes a common form of conformers.

In chemistry, a molecule experiences strain when its chemical structure undergoes some stress which raises its internal energy in comparison to a strain-free reference compound. The internal energy of a molecule consists of all the energy stored within it. A strained molecule has an additional amount of internal energy which an unstrained molecule does not. This extra internal energy, or strain energy, can be likened to a compressed spring. Much like a compressed spring must be held in place to prevent release of its potential energy, a molecule can be held in an energetically unfavorable conformation by the bonds within that molecule. Without the bonds holding the conformation in place, the strain energy would be released.

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

Biphenyl is an organic compound that forms colorless crystals. Particularly in older literature, compounds containing the functional group consisting of biphenyl less one hydrogen may use the prefixes xenyl or diphenylyl.

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

Cyclohexanone is the organic compound with the formula (CH2)5CO. The molecule consists of six-carbon cyclic molecule with a ketone functional group. This colorless oily liquid has a sweet odor reminiscent of benzaldehyde. Over time, samples of cyclohexanone assume a pale yellow color.

<span class="mw-page-title-main">Ring strain</span> Instability in molecules with bonds at unnatural angles

In organic chemistry, ring strain is a type of instability that exists when bonds in a molecule form angles that are abnormal. Strain is most commonly discussed for small rings such as cyclopropanes and cyclobutanes, whose internal angles are substantially smaller than the idealized value of approximately 109°. Because of their high strain, the heat of combustion for these small rings is elevated.

<span class="mw-page-title-main">Hydroperoxide</span> Class of chemical compounds

Hydroperoxides or peroxols are compounds of the form ROOH, where R stands for any group, typically organic, which contain the hydroperoxy functional group. Hydroperoxide also refers to the hydroperoxide anion and its salts, and the neutral hydroperoxyl radical (•OOH) consist of an unbond hydroperoxy group. When R is organic, the compounds are called organic hydroperoxides. Such compounds are a subset of organic peroxides, which have the formula ROOR. Organic hydroperoxides can either intentionally or unintentionally initiate explosive polymerisation in materials with unsaturated chemical bonds.

In organic chemistry, a ring flip is the interconversion of cyclic conformers that have equivalent ring shapes that results in the exchange of nonequivalent substituent positions. The overall process generally takes place over several steps, involving coupled rotations about several of the molecule's single bonds, in conjunction with minor deformations of bond angles. Most commonly, the term is used to refer to the interconversion of the two chair conformers of cyclohexane derivatives, which is specifically referred to as a chair flip, although other cycloalkanes and inorganic rings undergo similar processes.

<span class="mw-page-title-main">Cyclic compound</span> Molecule with a ring of bonded atoms

A cyclic compound is a term for a compound in the field of chemistry in which one or more series of atoms in the compound is connected to form a ring. Rings may vary in size from three to many atoms, and include examples where all the atoms are carbon, none of the atoms are carbon, or where both carbon and non-carbon atoms are present. Depending on the ring size, the bond order of the individual links between ring atoms, and their arrangements within the rings, carbocyclic and heterocyclic compounds may be aromatic or non-aromatic; in the latter case, they may vary from being fully saturated to having varying numbers of multiple bonds between the ring atoms. Because of the tremendous diversity allowed, in combination, by the valences of common atoms and their ability to form rings, the number of possible cyclic structures, even of small size numbers in the many billions.

<span class="mw-page-title-main">Allylic strain</span> Type of strain energy in organic chemistry

Allylic strain in organic chemistry is a type of strain energy resulting from the interaction between a substituent on one end of an olefin with an allylic substituent on the other end. If the substituents are large enough in size, they can sterically interfere with each other such that one conformer is greatly favored over the other. Allylic strain was first recognized in the literature in 1965 by Johnson and Malhotra. The authors were investigating cyclohexane conformations including endocyclic and exocylic double bonds when they noticed certain conformations were disfavored due to the geometry constraints caused by the double bond. Organic chemists capitalize on the rigidity resulting from allylic strain for use in asymmetric reactions.

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

Quinuclidine is an organic compound with the formula HC(C2H4)3N. It is a bicyclic amine that can be viewed as a tied back version of triethylamine. It is a colorless solid. It is used as a reagent (base) and catalyst. It can be prepared by reduction of quinuclidone and has great utility in the Cormas-Grisius Electrophilic Benzene Addition reaction. When protonated, Quinuclidine's heterocyclic structure allows its amine group to serve as a strong electrophile in the Cormas-Grisius Electrophilic Benzene Addition.

A-values are numerical values used in the determination of the most stable orientation of atoms in a molecule, as well as a general representation of steric bulk. A-values are derived from energy measurements of the different cyclohexane conformations of a monosubstituted cyclohexane chemical. Substituents on a cyclohexane ring prefer to reside in the equatorial position to the axial. The difference in Gibbs free energy (ΔG) between the higher energy conformation and the lower energy conformation is the A-value for that particular substituent.

<span class="mw-page-title-main">Benzene</span> Hydrocarbon compound

Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar hexagonal ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, benzene is classed as a hydrocarbon.

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

Methylcyclopentane is an organic compound with the chemical formula CH3C5H9. It is a colourless, flammable liquid with a faint odor. It is a component of the naphthene fraction of petroleum usually obtained as a mixture with cyclohexane. It is mainly converted in naphthene reformers to benzene.

References

  1. ↑ "Front Matter". Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. pp. P001–P004. doi:10.1039/9781849733069-FP001. ISBN   978-0-85404-182-4.
  2. ↑ "Hexanaphthene". dictionary.com. Archived from the original on 2018-02-12.
  3. 1 2 3 4 5 NIOSH Pocket Guide to Chemical Hazards. "#0163". National Institute for Occupational Safety and Health (NIOSH).
  4. 1 2 "Cyclohexane". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  5. ↑ Campbell, M. Larry (2011). "Cyclohexane". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a08_209.pub2. ISBN   978-3527306732.
  6. ↑ "Standard Abbreviations and Acronyms" (PDF). The Journal of Organic Chemistry. Archived from the original (PDF) on 1 Aug 2018.
  7. ↑ Weissermel, Klaus; Arpe, Hans-Jürgen (2008-07-11). Industrial Organic Chemistry. John Wiley & Sons. p. 345. ISBN   978-3-527-61459-2.
  8. ↑ Ceresana. "Benzene - Study: Market, Analysis, Trends 2021 - Ceresana". www.ceresana.com. Archived from the original on 21 December 2017. Retrieved 4 May 2018.
  9. 1 2 Michael Tuttle Musser (2005). "Cyclohexanol and Cyclohexanone". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a08_217. ISBN   978-3527306732.
  10. ↑ Warnhoff, E. W. (1996). "The Curiously Intertwined Histories of Benzene and Cyclohexane". J. Chem. Educ. 73 (6): 494. Bibcode:1996JChEd..73..494W. doi:10.1021/ed073p494.
  11. ↑ Bertholet (1867). "Nouvelles applications des méthodes de réduction en chimie organique" [New applications of reduction methods in organic chemistry]. Bulletin de la Société Chimique de Paris (in French). series 2 (7): 53–65.
  12. ↑ Bertholet (1868). "Méthode universelle pour réduire et saturer d'hydrogène les composés organiques" [Universal method for reducing and saturating organic compounds with hydrogen]. Bulletin de la Société Chimique de Paris (in French). series 2 (9): 8–31. En effet, la benzine, chauffée à 280° pendant 24 heures avec 80 fois son poids d'une solution aqueuse saturée à froid d'acide iodhydrique, se change à peu près entièrement en hydrure d'hexylène, C12H14, en fixant 4 fois son volume d'hydrogène: C12H6 + 4H2 = C12H14 … Le nouveau carbure formé par la benzine est un corps unique et défini: il bout à 69°, et offre toutes les propriétés et la composition de l'hydrure d'hexylène extrait des pétroles.[In effect, benzene, heated to 280° for 24 hours with 80 times its weight of an aqueous solution of cold saturated hydroiodic acid, is changed almost entirely into hydride of hexylene, C12H14, [Note: this formula for hexane (C6H14) is wrong because chemists at that time used the incorrect atomic mass for carbon.] by fixing [i.e., combining with] 4 times its volume of hydrogen: C12H6 + 4H2 = C12H14 The new carbon compound formed by benzene is a unique and well-defined substance: it boils at 69° and presents all the properties and the composition of hydride of hexylene extracted from oil.)]
  13. ↑ Adolf Baeyer (1870). "Ueber die Reduction aromatischer Kohlenwasserstoffe durch Jodphosphonium" [On the reduction of aromatic compound by phosphonium iodide [H4IP]]. Annalen der Chemie und Pharmacie. 55: 266–281. Bei der Reduction mit Natriumamalgam oder Jodphosphonium addiren sich im höchsten Falle sechs Atome Wasserstoff, und es entstehen Abkömmlinge, die sich von einem Kohlenwasserstoff C6H12 ableiten. Dieser Kohlenwasserstoff ist aller Wahrscheinlichkeit nach ein geschlossener Ring, da seine Derivate, das Hexahydromesitylen und Hexahydromellithsäure, mit Leichtigkeit wieder in Benzolabkömmlinge übergeführt werden können.[During the reduction [of benzene] with sodium amalgam or phosphonium iodide, six atoms of hydrogen are added in the extreme case, and there arise derivatives, which derive from a hydrocarbon C6H12. This hydrocarbon is in all probability a closed ring, since its derivatives — hexahydromesitylene [1,3,5 - trimethyl cyclohexane] and hexahydromellithic acid [cyclohexane-1,2,3,4,5,6-hexacarboxylic acid] — can be converted with ease again into benzene derivatives.]
  14. ↑ Price, D. M. (1995). "Temperature Calibration of Differential Scanning Calorimeters". Journal of Thermal Analysis. 45 (6): 1285–1296. doi:10.1007/BF02547423. S2CID   97402835.
  15. 1 2 Mayer, J.; Urban, S.; Habrylo, S.; Holderna, K.; Natkaniec, I.; Würflinger, A.; Zajac, W. (1991). "Neutron Scattering Studies of C6H12 and C6D12 Cyclohexane under High Pressure". Physica Status Solidi B. 166 (2): 381. Bibcode:1991PSSBR.166..381M. doi:10.1002/pssb.2221660207.
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