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

bicyclic 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 of the ring ...

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

, is an industrial

solvent A solvent (from the Latin language, Latin ''wikt:solvo#Latin, solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a Solution (chemistry), solution. A solvent is usually a liquid but can also be a solid, a gas ...

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

resin A resin is a solid or highly viscous liquid that can be converted into a polymer. Resins may be biological or synthetic in origin, but are typically harvested from plants. Resins are mixtures of organic compounds, predominantly terpenes. Commo ...

s 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 Chirality () is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable fro ...

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 Cyclohexane is a cycloalkane with the molecular formula . 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). Cyclohexan ...

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 and living organisms. It is a broad natural science that encompasses a wide range of fields and unifying principles that explain the structure, function, growth, History of life, origin, evolution, and ...

this fixation is widely used in the

steroid A steroid is an organic compound with four fused compound, fused rings (designated A, B, C, and D) arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes t ...

skeleton to construct

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

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

Reactions

Oxygenation of decalin gives the tertiary

hydroperoxide Hydroperoxides or peroxols are Chemical compound, compounds of the form ROOH, where R stands for any group, typically Organic compound, organic, which contain the hydroperoxy functional group (). Hydroperoxide also refers to the hydroperoxide anio ...

, which rearranges via hydroxycyclodecanone to , a precursor to sebacic acid. Decalin is the saturated analog of

naphthalene Naphthalene is an organic compound with formula . It is the simplest polycyclic aromatic hydrocarbon, and is a white Crystal, crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 Parts-per notation ...

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 redox, reduce or Saturated ...

in the presence of a

catalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

. This interconversion has been considered in the context of hydrogen storage.

Derivation

Treatment of

in a fused state with hydrogen in the presence of a copper or nickel catalyst.

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 ≥ 2. Terpenes are major biosynthetic building blocks. Comprising more than 30,000 compounds, these unsaturated hydrocarbons are produced predomi ...

-derived precursors or

polyketide In organic chemistry, polyketides are a class of natural products derived from a Precursor (chemistry), precursor molecule consisting of a Polymer backbone, chain of alternating ketone (, or Carbonyl reduction, its reduced forms) and Methylene gro ...

Safety

Decalin easily forms

explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An ex ...

s upon storage in the presence of air.

References

{{Authority control Hydrocarbon solvents Bicycloalkanes