Tetralin

Tetralin (1,2,3,4-tetrahydronaphthalene) is a hydrocarbon having the chemical formula C10H12. It is a partially hydrogenated derivative of naphthalene. It is a colorless liquid that is used as a hydrogen-donor solvent.

Production
Tetralin is produced by the catalytic hydrogenation of naphthalene.



Although nickel catalysts are traditionally employed, many variations have been evaluated. Over-hydrogenation converts tetralin into decahydronaphthalene (decalin). Rarely encountered is dihydronaphthalene (dialin).

Laboratory methods
In a classic named reaction called the Darzens tetralin synthesis, named for Auguste Georges Darzens (1926), derivatives can be prepared by intramolecular electrophilic aromatic substitution reaction of a 1-aryl-pent-4-ene using concentrated sulfuric acid,



Uses
Tetralin is used as a hydrogen-donor solvent, for example in coal liquifaction. It functions as a source of H2, which is transferred to the coal. The partially hydrogenated coal is more soluble.

It has been used in sodium-cooled fast reactors as a secondary coolant to keep sodium seals around pump impellers solidified; however its use has been superseded by NaK.

It is also used for the laboratory synthesis of hydrogen bromide:
 * C10H12 + 4 Br2 → C10H8Br4 + 4 HBr

The facility of this reaction is in part a consequence of the moderated strength of the benzylic C-H bonds.

Safety
(rats, oral) is 2.68 g/kg. Tetralin induces methemoglobinemia.