Decalin

Decalin (decahydronaphthalene, also known as bicyclo[4.4.0]decane and sometimes decaline),[3] 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.[4] It is the saturated analog of naphthalene and can be prepared from it by hydrogenation in the presence of a catalyst. Decalin easily forms explosive[5] organic peroxides upon storage in the presence of air.[6][7]

Decalin
Names
Preferred IUPAC name
Decahydronaphthalene[1]
Other names
Bicyclo[4.4.0]decane[1]
Decalin
Identifiers
3D model (JSmol)
878165
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.001.861
EC Number
  • 202-046-9, 207-770-9, 207-771-4
185147
RTECS number
  • QJ3150000
UNII
UN number 1147
Properties
C10H18
Molar mass 138.25 g/mol
Appearance colorless liquid
Density 0.896 g/cm3
Melting point trans: −30.4 °C (−22.7 °F, 242.7 K)
cis: −42.9 °C (−45.2 °F, 230.3 K)[2]
Boiling point trans: 187 °C (369 °F)
cis: 196 °C (384 °F)
Insoluble
  • −107.7·10−6 cm3/mol (trans)
  • −107.0·10−6 cm3/mol (cis)
1.481
Hazards
Safety data sheet Decalin MSDS
GHS pictograms
GHS Signal word Danger
H226, H302, H305, H314, H318, H331, H332, H400, H410, H411
P210, P233, P240, P241, P242, P243, P260, P261, P264, P271, P273, P280, P301+310, P301+330+331, P303+361+353, P304+312, P304+340, P305+351+338, P310, P311, P312, P321, P331, P363, P370+378
Flash point 57 °C (135 °F; 330 K)
250 °C (482 °F; 523 K)
Related compounds
Related compounds
 Naphthalene; Tetralin
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

Isomers

Decahydronaphthalene occurs in cis and trans forms. The trans form is energetically more stable because of fewer steric interactions. cis-Decalin is a chiral molecule without a chiral center; it has a two-fold rotational symmetry axis, but no reflective symmetry. However, the chirality is canceled through a chair-flipping process that turns the molecule into its mirror image.

  • 1: trans (left) and cis (right) isomers
  • 2:
    ball-and-stick model of cis-decalin
  • 3:
    trans-decalin
  • 4:
    cis-decalin ring-flip
  • 5: Half a decalin molecule: cyclohexane in chair conformation. Axial positions are shown in red, while those in equatorial positions are in blue.
  • 6: Androstanediol, a biomolecule with three trans fused six membered rings (and an also trans fused five membered one)

trans-Decalin

The only possible way to join the two six-membered rings in the trans position means the second ring needs to start from two equatorial bonds (blue) of the first ring. A six-membered ring does not offer sufficient space to start out on an axial position (upwards), and reach the axial position of the neighboring carbon atom, which then will be on the downwards side of the molecule (see the model of cyclohexane in figure 5). The structure is conformationally frozen, rather than having the ability to undergo the chair flip as in the cis isomer. In biology this fixation is widely used in the steroid skeleton to construct molecules (such as figure 6) that play a key role in the signalling between distantly separated cells.

Reactions

Oxygenation of decalin give the tertiary hydroperoxide, which rearranges to cyclodecenone, a precursor to sebacic acid.[8]

See also

References
  1. Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. pp. 33, 394, 601. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  2. Haynes, William M. (2010). Handbook of Chemistry and Physics (91 ed.). Boca Raton, Florida, USA: CRC Press. p. 3-134. ISBN 978-1-43982077-3.
  3. "Dictionary.com".
  4. "Fuel Additive Product". Archived from the original on 2009-03-12.
  5. "PDF – Surrogate JP-8 Aviation Fuel Study – Alessandro Agosta Thesis Drexel University" (PDF). Archived from the original (PDF) on 2010-06-19.
  6. "Inchem.org Data".
  7. "MSDS Sheet – JT Baker".
  8. Griesbaum, Karl; Behr, Arno; Biedenkapp, Dieter; Voges, Heinz-Werner; Garbe, Dorothea; Paetz, Christian; Collin, Gerd; Mayer, Dieter; Höke (2000). "Hydrocarbons". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a13_227.
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