Biphenyl

Biphenyl is an aromatic hydrocarbon composed of two benzene rings joined by a single carbon–carbon bond. Its molecular formula is C₁₂H₁₀.

Benzene: A six-carbon aromatic hydrocarbon with molecular formula C₆H₆ and a planar ring of delocalized electrons. Each of biphenyl’s two rings has benzene’s six-carbon aromatic framework.
Steric hindrance: Reduced molecular stability or reaction rate caused by the spatial crowding of atoms or groups. The ortho hydrogens on biphenyl’s rings crowd one another and favor a twisted geometry.
Biphenyl process: An industrial method for producing biphenyl by coupling benzene molecules at high temperature. This process makes biphenyl through the direct coupling of benzene.
Terphenyl: An aromatic hydrocarbon made of three benzene rings linked by carbon–carbon bonds. Terphenyl extends biphenyl’s linked-ring structure by adding a third benzene ring.
Phenyl group: A C₆H₅ substituent formed by removing one hydrogen atom from benzene. Biphenyl consists of two phenyl groups joined at their substituted carbon atoms.
Ortho effect: A set of steric and electronic effects caused by substituents adjacent to a functional group on an aromatic ring. Ortho substituents can intensify crowding between biphenyl’s rings and alter rotation.
Diphenyl oxide: An aromatic ether consisting of two phenyl groups linked by an oxygen atom. Diphenyl oxide is paired with biphenyl in high-temperature heat-transfer fluids.
Naphthalene: A fused-ring aromatic hydrocarbon composed of two joined benzene-like rings, with formula C₁₀H₈. Unlike biphenyl, naphthalene has fused rings that share two adjacent carbon atoms.
Aromaticity: The unusual stability and electronic structure associated with cyclic, conjugated systems meeting aromaticity criteria. Aromaticity explains the stability of each ring in biphenyl.
Atropisomerism: Stereoisomerism arising when rotation around a single bond is sufficiently hindered to make conformers isolable. Bulky ortho substituents can lock biphenyl derivatives into distinct, isolable forms.

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PhenanthreneCompared with: Its rings are connected, not fused as they are in phenanthrene.