decalin

Decalin, or decahydronaphthalene, is a saturated bicyclic hydrocarbon with the formula C10H18. It is the hydrogenated product of naphthalene and consists of two cyclohexane rings fused together.

Decalin exists as two stereoisomers, cis-decalin and trans-decalin, which differ in the arrangement of substituents at the ring junction. Both isomers feature chair conformations for each ring, but the fusion geometry leads to different conformational rigidity and physical properties. Trans-decalin is typically more rigid due to its trans fusion.

Production and properties: Decalin is typically prepared by catalytic hydrogenation of naphthalene or related aromatic precursors under high hydrogen pressure with metal catalysts. It is a colorless, high-boiling liquid that is immiscible with water and is relatively nonpolar. The two isomers have distinct physical properties that can influence their behavior as solvents.

Applications: Decalin is used primarily as a nonpolar solvent in organic synthesis, particularly for high-temperature reactions where more common solvents would evaporate. It also serves as a chemical intermediate and as a reference hydrocarbon in some analytical applications. The cis and trans isomers can be separated and used when specific physical properties are required.

Safety: Decalin is flammable and should be handled with standard laboratory precautions, including good ventilation and avoidance of heat sources or flames. It can cause irritation to skin and eyes on contact and should be stored away from oxidizers. As with many hydrocarbons, inhalation should be minimized.