Decalin (decahydronaphthalene, also known as bicyclo .4.0ecane and sometimes decaline), a

bicyclic In chemistry, a bicyclic molecule () is a molecule that features two joined rings. Bicyclic structures occur widely, for example in many biologically important molecules like α-thujene and camphor. A bicyclic compound can be carbocyclic (all ...

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...

, is an industrial

solvent A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

. A colorless liquid with an aromatic odor, it is used as a solvent for many

resin In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on n ...

s or fuel additives.

Isomers

Decalin occurs in ''cis'' and ''trans''

forms Form is the shape, visual appearance, or configuration of an object. In a wider sense, the form is the way something happens. Form also refers to: *Form (document), a document (printed or electronic) with spaces in which to write or enter data * ...

. 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. Image:Cis-trans isomerism of decahydronaphthalene.svg, Image:cis-decalin double chair.png, 2: Image:trans-decalin double chair.png, 3: File:Cisdecalin conformations.png, 4:

''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 Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...

this fixation is widely used in the steroid skeleton to construct

molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioche ...

s (such as figure 6) that play a key role in the signalling between distantly separated cells.

Reactions

Oxygenation of decalin give the tertiary

hydroperoxide Hydroperoxides or peroxols are compounds containing the hydroperoxide functional group (ROOH). If the R is organic, the compounds are called organic hydroperoxides. Such compounds are a subset of organic peroxides, which have the formula ROOR. ...

, which rearranges to cyclodecenone, a precursor to

sebacic acid Sebacic acid is a naturally occurring dicarboxylic acid with the chemical formula . It is a white flake or powdered solid. ''Sebaceus'' is Latin for tallow candle, ''sebum'' is Latin for tallow, and refers to its use in the manufacture of candles. ...

. Decalin is the saturated analog of naphthalene and can be prepared from it by

hydrogenation Hydrogenation is a chemical reaction between molecular hydrogen (H2) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organ ...

in the presence of a

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

. 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 Terpenes () are a class of natural products consisting of compounds with the formula (C5H8)n for n > 1. Comprising more than 30,000 compounds, these unsaturated hydrocarbons are produced predominantly by plants, particularly conifers. Terpenes ...

-derived precursors or

polyketide Polyketides are a class of natural products derived from a precursor molecule consisting of a chain of alternating ketone (or reduced forms of a ketone) and methylene groups: (-CO-CH2-). First studied in the early 20th century, discovery, biosynth ...

Safety

Decalin easily forms explosive

s upon storage in the presence of air.

References