decalen

Decalen, commonly spelled decalin, refers to decahydronaphthalene, a saturated bicyclic hydrocarbon with the formula C10H18. It consists of two cyclohexane rings fused to form a bicyclo[4.4.0]decane skeleton and is the hydrogenated product of naphthalene. There are two stereoisomers: cis-decalin and trans-decalin, which are diastereomers. In cis-decalin, the hydrogens on the ring junction are on the same face; in trans-decalin they lie on opposite faces. The trans isomer is more conformationally rigid due to its ring fusion.

Production and occurrence: Decalin is produced industrially by catalytic hydrogenation of naphthalene or other aromatics under high hydrogen pressure using metal catalysts. It is not typically found as a natural product but occurs in small amounts in certain petroleum fractions as a stable hydrocarbon component.

Physical properties: It is a colorless, high-boiling, nonpolar liquid. It is insoluble in water and miscible with many nonpolar solvents. It is relatively thermally stable but can be dehydrogenated catalytically to naphthalene under suitable conditions.

Applications: Decalin serves as a nonpolar solvent for high-temperature organic reactions and as a chemical intermediate in fragrance and pharmaceutical manufacturing. In conformational analysis, trans-decalin is often cited as an example of a rigid bicyclic system.

Safety: It is flammable; vapors may form explosive mixtures with air. It should be handled in well-ventilated areas away from heat, sparks, and open flames, with appropriate protective equipment.