biphenyl

Biphenyl, also known as diphenyl, is an organic compound with the formula C12H10. It consists of two phenyl rings (benzene rings) connected by a single carbon–carbon bond. Because the bond allows rotation, the two rings can adopt various dihedral angles; in unsubstituted biphenyl, the rings are twisted relative to one another, and the molecule is non-planar in the ground state. The compound is nonpolar and hydrophobic.

Biphenyl is a solid at room temperature, with a melting point around 70 °C and a boiling point near 255 °C. It is sparingly soluble in water and readily soluble in many organic solvents such as benzene, toluene, and chloroform. It is relatively chemically stable under ambient conditions but can undergo oxidation or electrophilic aromatic substitution on the rings under appropriate conditions.

Occurrence and production: In industry, biphenyl is produced by various catalytic coupling methods that join two phenyl units, such as Ullmann-type or related cross-coupling reactions starting from simple aryl halides or phenyl derivatives. It also occurs in small amounts in coal tar and other fossil fuels as a trace hydrocarbon.

Uses: Biphenyl serves as a building block in the synthesis of more complex aromatics, including dyes, polymers, and liquid-crystal materials. It is also used as a reference compound or solvent in analytical chemistry and as a nonpolar model substrate for studying biaryl bond rotation. Safety: It has relatively low acute toxicity but should be handled with standard laboratory precautions. It may cause skin or eye irritation and can form hazardous oxidized products on prolonged exposure.