Biphenyl and its uses

Biphenyl is an organic compound that forms colorless crystals.In particular, in earlier literature, compounds containing a functional group consisting of biphenyl minus one hydrogen (where it is attached) could use the prefix xenyl or diphenyl.It has a particularly pleasant smell. Biphenyl is an aromatic hydrocarbon with the molecular formula (C6H5)2.It is famous as a starting material for the production of polychlorinated biphenyls (PCBs), which have been widely used as dielectric fluids and heat transfer agents.Biphenyl is also an intermediate in the production of many other organic compounds such as emulsifiers, optical brighteners, crop protection products and plastics.Biphenyl is insoluble in water but soluble in typical organic solvents.The biphenyl molecule consists of two connected benzene rings.

Reactions and uses 

Due to the lack of functional groups, biphenyl is rather inactive, which is the basis for its main applications. In the laboratory, biphenyl is mainly used as a heat transfer agent as a eutectic mixture with diphenyl ether.This mixture is stable at 400 °C.Biphenyl does undergo sulfonation followed by alkaline hydrolysis to produce p-hydroxybiphenyl and p,p’-dihydroxybiphenyl, which are useful fungicides.In other substitution reactions, it undergoes halogenation. PCBs were once a popular pesticide.Lithium biphenyl contains a radical anion and is highly reducing (-3.1 V vs Fc+/0).Several solvates of the alkali metal salts of the biphenyl anion have been characterized by X-ray crystallography.These salts are usually prepared in situ and are versatile reducing agents.Lithium biphenyl has several advantages over the related lithium naphthenes.Related to Li/biphenyl are derivatives with two tert-butyl groups on biphenyl.

Biological aspects

Biphenyl prevents the growth of mold and fungi and is therefore used as a preservative (E230, in combination with E231, E232 and E233), especially for preserving citrus fruit during transport.It is no longer approved as a food additive by the EU.It is slightly toxic but biodegrades by conversion into nontoxic compounds. Some bacteria are capable of hydroxylating biphenyls and their polychlorinated biphenyls (PCBs).It is part of the active group of the antibiotic oritavancin.