Biphenyl

Biphenyl (or diphenyl or phenyl benzene or 1,1'-biphenyl or lemonene) is a solid organic compound that forms colorless to yellowish crystals. It has a distinctively pleasant smell. Biphenyl is an aromatic hydrocarbon with a molecular formula C₁₂H₁₀. Biphenyl is notable as a starting material for the production of polychlorinated biphenyls (PCB's), which were once widely used as dielectric fluids and heat transfer agents. Biphenyl is also an intermediate for the production of a host of other organic compounds such as emulsifiers, optical brighteners, crop protection products, and plastics.

1 Properties
2 Stereochemistry
3 Biological aspects
4 Reference
5 External links

[edit] Properties

Biphenyl occurs naturally in coal tar, crude oil, and natural gas and can be produced from these sources by distillation. Biphenyl is insoluble in water, but soluble in typical organic solvents. The biphenyl molecule consists of two connected benzene rings, without any additional functionalization, and is therefore not very reactive. The flashpoint is 113 °C and the autoignition temperature is 540 °C. Substituted biphenyls can be prepared synthetically by various methods including the Suzuki reaction and the Ullmann reaction.

[edit] Stereochemistry

Rotation about the single bond in biphenyl, and especially its ortho-substituted derivatives, is sterically hindered. For this reason, some substituted biphenyls show atropisomerism; that is, the individual C₂-symmetric-isomers are optically stable. Some derivatives, as well as related molecules such as BINAP, find application as ligands in asymmetric synthesis

[edit] Biological aspects

Biphenyl prevents the growth of molds and fungus, and is therefore used as a preservative (E230, in combination with E231, E232 and E233), particularly in the preservation of citrus fruits during transportation.

It is degraded biologically.