What Is Biphenyl?
Biphenyl is an aromatic hydrocarbon consisting of two benzene rings joined by a single bond. It appears as a colorless or white solid and is almost insoluble in water but dissolves in acetone and alcohol. While some biphenyl derivatives have a wide range of applications, others are highly toxic and require careful handling and disposal.
Properties of Biphenyl
1. Appearance:
Colorless or white crystalline substance, sometimes in flake form.
2. Solubility:
Insoluble in water, and soluble in organic solvents like acetone, ethanol, toluene, and xylene.
3. Structure:
Biphenyl adopts a planar structure at room temperature but forms a twisted conformation when cooled below its phase transition temperature due to steric hindrance.
4. Physical Properties:
- Melting Point: 155-162°F
- Boiling Point: 490-493°F
- Specific Gravity: 0.992
Uses of Biphenyl
Biphenyl is used as a fungicide, synthetic resin, heat transfer medium, and raw material. In Japan, it is used less frequently in citrus fruits due to biphenyl-resistant bacteria. Biphenyl is also added to lithium-ion battery electrolytes as an overcharge inhibitor.
Polychlorinated biphenyls (PCBs), derivatives of biphenyl, were previously used in insulators, heat transfer media, and plasticizers but were banned due to their adverse health effects and environmental impact.
Other Information on Biphenyl
1. Synthesis Methods:
Biphenyl can be synthesized through various methods, including the Ullmann reaction, heating benzene in a red-hot tube, and photolysis of benzene bromide.
2. Safety:
Biphenyl is an eye irritant and a carcinogen. Long-term exposure can affect the liver, kidney, and nervous system. Safety precautions, including protective gear, are necessary when handling biphenyl and its derivatives.