bifenyler

Bifenyler, or biphenyls in English, are a class of organic compounds consisting of two phenyl rings linked by a single carbon–carbon bond. The simplest member is biphenyl (C12H10). Substituted bifenyler have various groups on one or both rings, giving a wide range of physical properties and applications.

Structure and properties: The two rings in bifenyler can rotate about the aryl–aryl bond, allowing conformational flexibility. In many substituted biphenyls, steric hindrance from bulky ortho groups can hinder rotation, leading to atropisomerism. The compounds are typically nonpolar and hydrophobic, with melting and boiling points that depend on substitution. Unsubstituted biphenyl has a melting point around 70 °C and a boiling point near 256 °C. Solubility in water is low, while solubility in organic solvents is high.

Synthesis: Bifenyler are commonly prepared by cross-coupling reactions. Suzuki-Miyaura coupling between aryl boronates and aryl halides is widely used, as are Ullmann-type copper-catalyzed or related couplings. Other routes include coupling of phenyl derivatives under various catalytic conditions. Industrial production often targets substituted biphenyls for specific applications.

Applications: Unsubstituted biphenyl serves as a nonpolar solvent and a high-temperature heat-transfer fluid in some industrial contexts. Substituted bifenyler are used as intermediates in the synthesis of dyes, polymers, pharmaceuticals, and agrochemicals. Some biphenyl derivatives also function as ligands or building blocks in catalytic systems.

Safety and environmental aspects: The parent biphenyl is of relatively low acute toxicity but can cause irritation. Many substituted or chlorinated biphenyls are hazardous or persistent environmental pollutants, so handling, storage, and disposal follow strict safety and regulatory guidelines.