Chemistry:Decalin

Decalin

Names
Preferred IUPAC name Decahydronaphthalene
Other names Bicyclo[4.4.0]decane Decalin
Identifiers
CAS Number	91-17-8 Y
3D model (JSmol)	Interactive image cis: Interactive image trans: Interactive image
Beilstein Reference	878165
ChEBI	CHEBI:38853 Y cis: CHEBI:38860 trans: CHEBI:38863
ChEMBL	ChEMBL1491920
ChemSpider	6777 Y
EC Number	202-046-9, 207-770-9, 207-771-4
Gmelin Reference	185147
PubChem CID	7044
RTECS number	QJ3150000
UNII	88451Q4XYF
UN number	1147
InChI InChI=1S/C10H18/c1-2-6-10-8-4-3-7-9(10)5-1/h9-10H,1-8H2 Y Key: NNBZCPXTIHJBJL-UHFFFAOYSA-N Y InChI=1/C10H18/c1-2-6-10-8-4-3-7-9(10)5-1/h9-10H,1-8H2 Key: NNBZCPXTIHJBJL-UHFFFAOYAH
SMILES C1CCC2CCCCC2C1 cis: C1CC[C@H]2CCCC[C@H]2C1 trans: C1CC[C@H]2CCCC[C@@H]2C1
Properties
Chemical formula	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)
Boiling point	trans: 187 °C (369 °F) cis: 196 °C (384 °F)
Solubility in water	Insoluble
Magnetic susceptibility (χ)	−107.7·10−6 cm3/mol (trans) −107.0·10−6 cm3/mol (cis)
Refractive index (nD)	1.481
Hazards
Safety data sheet	Decalin MSDS
GHS pictograms
GHS Signal word	Danger
GHS hazard statements	H226, H302, H305, H314, H331, H332, H410, H411
GHS precautionary statements	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)
Autoignition temperature	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

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Decalin (decahydronaphthalene, also known as bicyclo[4.4.0]decane and sometimes decaline), 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.

Isomers

Decalin 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

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. It does not have the ability to undergo a 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 gives the tertiary hydroperoxide, which rearranges to cyclodecenone, a precursor to sebacic acid.

Decalin is the saturated analog of naphthalene and can be prepared from it by hydrogenation in the presence of a catalyst. This interconversion has been considered in the context of hydrogen storage.

Occurrence

Decalin itself is rare in nature but several decalin derivatives are known. They arise via terpene-derived precursors or polyketides.

Safety

Decalin easily forms explosive hydroperoxides upon storage in the presence of air.

See also

• Perfluorodecalin
• Tetralin
• Dialin
• Naphthalene