Biphenyl
Overview
 
Biphenyl is an organic compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 that forms colorless crystals. It has a distinctively pleasant smell. Biphenyl is an aromatic hydrocarbon
Aromatic hydrocarbon
An aromatic hydrocarbon or arene is a hydrocarbon with alternating double and single bonds between carbon atoms. The term 'aromatic' was assigned before the physical mechanism determining aromaticity was discovered, and was derived from the fact that many of the compounds have a sweet scent...

 with a molecular formula (C6H5)2. It is notable as a starting material for the production of polychlorinated biphenyl
Polychlorinated biphenyl
Polychlorinated biphenyls are a class of organic compounds with 2 to 10 chlorine atoms attached to biphenyl, which is a molecule composed of two benzene rings. The chemical formula for PCBs is C12H10-xClx...

s (PCBs), which were once widely used as dielectric
Dielectric
A dielectric is an electrical insulator that can be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material, as in a conductor, but only slightly shift from their average equilibrium positions causing dielectric...

 fluids and heat transfer
Heat transfer
Heat transfer is a discipline of thermal engineering that concerns the exchange of thermal energy from one physical system to another. Heat transfer is classified into various mechanisms, such as heat conduction, convection, thermal radiation, and phase-change transfer...

 agents. Biphenyl is also an intermediate for the production of a host of other organic compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

s such as emulsifiers, optical brightener
Optical brightener
Optical brighteners, optical brightening agents , fluorescent brightening agents or fluorescent whitening agents are dyes that absorb light in the ultraviolet and violet region of the electromagnetic spectrum, and re-emit light in the blue region...

s, crop protection
Insecticide
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...

 products, and plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

s.
Biphenyl occurs naturally in coal tar
Coal tar
Coal tar is a brown or black liquid of extremely high viscosity, which smells of naphthalene and aromatic hydrocarbons. Coal tar is among the by-products when coal iscarbonized to make coke or gasified to make coal gas...

, crude oil, and natural gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...

 and can be isolated from these sources via distillation
Distillation
Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....

.
Encyclopedia
Biphenyl is an organic compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

 that forms colorless crystals. It has a distinctively pleasant smell. Biphenyl is an aromatic hydrocarbon
Aromatic hydrocarbon
An aromatic hydrocarbon or arene is a hydrocarbon with alternating double and single bonds between carbon atoms. The term 'aromatic' was assigned before the physical mechanism determining aromaticity was discovered, and was derived from the fact that many of the compounds have a sweet scent...

 with a molecular formula (C6H5)2. It is notable as a starting material for the production of polychlorinated biphenyl
Polychlorinated biphenyl
Polychlorinated biphenyls are a class of organic compounds with 2 to 10 chlorine atoms attached to biphenyl, which is a molecule composed of two benzene rings. The chemical formula for PCBs is C12H10-xClx...

s (PCBs), which were once widely used as dielectric
Dielectric
A dielectric is an electrical insulator that can be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material, as in a conductor, but only slightly shift from their average equilibrium positions causing dielectric...

 fluids and heat transfer
Heat transfer
Heat transfer is a discipline of thermal engineering that concerns the exchange of thermal energy from one physical system to another. Heat transfer is classified into various mechanisms, such as heat conduction, convection, thermal radiation, and phase-change transfer...

 agents. Biphenyl is also an intermediate for the production of a host of other organic compound
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

s such as emulsifiers, optical brightener
Optical brightener
Optical brighteners, optical brightening agents , fluorescent brightening agents or fluorescent whitening agents are dyes that absorb light in the ultraviolet and violet region of the electromagnetic spectrum, and re-emit light in the blue region...

s, crop protection
Insecticide
An insecticide is a pesticide used against insects. They include ovicides and larvicides used against the eggs and larvae of insects respectively. Insecticides are used in agriculture, medicine, industry and the household. The use of insecticides is believed to be one of the major factors behind...

 products, and plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

s.

Properties

Biphenyl occurs naturally in coal tar
Coal tar
Coal tar is a brown or black liquid of extremely high viscosity, which smells of naphthalene and aromatic hydrocarbons. Coal tar is among the by-products when coal iscarbonized to make coke or gasified to make coal gas...

, crude oil, and natural gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...

 and can be isolated from these sources via distillation
Distillation
Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....

. It can also be synthesized by using a grignard reagent such as phenylmagnesium bromide
Phenylmagnesium bromide
Phenylmagnesium bromide, with the simplified formula , is a magnesium-containing organometallic compound. It is so commonly used that it is commercially available as a solution in diethyl ether or tetrahydrofuran . Phenylmagnesium bromide is a Grignard reagent...

 and reacting it with bromobenzene. Biphenyl is insoluble
Solubility
Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on...

 in water, but soluble in typical organic solvents. The biphenyl molecule consists of two connected phenyl rings. Lacking functional groups, it is fairly non-reactive. It will, however, participate in many of the reactions that are typical for benzene, for example, substitution
Electrophilic aromatic substitution
Electrophilic aromatic substitution EAS is an organic reaction in which an atom, usually hydrogen, appended to an aromatic system is replaced by an electrophile...

 reactions upon treatment with halogens in the presence of a Lewis acid.

Stereochemistry

Rotation about the single bond in biphenyl, and especially its ortho-substituted
Arene substitution patterns
Arene substitution patterns are part of organic chemistry IUPAC nomenclature and pinpoint the position of substituents other than hydrogen in relation to each other on an aromatic hydrocarbon.- Ortho, meta, and para substitution :...

 derivatives, is sterically hindered. For this reason, some substituted biphenyls show atropisomerism; that is, the individual C2-symmetric
Symmetry group
The symmetry group of an object is the group of all isometries under which it is invariant with composition as the operation...

-isomers are optically stable. Some derivatives, as well as related molecules such as BINAP
BINAP
BINAP is an abbreviation for the organophosphorus compound 2,2'-bis-1,1'-binaphthyl. This chiral ligand is widely used in asymmetric synthesis. It consists of a pair of 2-diphenylphosphinonaphthyl groups linked at the 1 and 1´ positions. This C2-symmetric framework lacks stereogenic atom, but...

, find application as ligand
Ligand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...

s in asymmetric synthesis. In the case of unsubstituted biphenyl, the equilibrium torsional angle is 44.4° and the torsional barriers are quite small, 6.0 kJ/mol at 0° and 6.5 kJ/mol at 90°. Adding ortho substituents greatly increases the barrier: in the case of the 2,2'-dimethyl derivative, the barrier is 17.4 kcal/mol (72.8 kJ/mol).

Biological aspects

Biphenyl prevents the growth of mold
Mold
Molds are fungi that grow in the form of multicellular filaments called hyphae. Molds are not considered to be microbes but microscopic fungi that grow as single cells called yeasts...

s and fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

, and is therefore used as a preservative
Preservative
A preservative is a naturally occurring or synthetically produced substance that is added to products such as foods, pharmaceuticals, paints, biological samples, wood, etc. to prevent decomposition by microbial growth or by undesirable chemical changes....

 (E230
E number
E numbers are number codes for food additives that have been assessed for use within the European Union . They are commonly found on food labels throughout the European Union. Safety assessment and approval are the responsibility of the European Food Safety Authority...

, in combination with E231, E232 and E233), particularly in the preservation of citrus
Citrus
Citrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...

 fruits during transportation.

It is mildly toxic, but can be degraded biologically by conversion into nontoxic compounds. Some bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 are able to hydroxylate biphenyl and its polychlorinated biphenyl
Polychlorinated biphenyl
Polychlorinated biphenyls are a class of organic compounds with 2 to 10 chlorine atoms attached to biphenyl, which is a molecule composed of two benzene rings. The chemical formula for PCBs is C12H10-xClx...

s (PCBs).

It is part of the active group in the antibiotic oritavancin
Oritavancin
Oritavancin is a novel semi-synthetic glycopeptide antibiotic being developed for the treatment of serious Gram-positive infections...

.

Biphenyl compounds

Substituted biphenyls can be prepared synthetically by various coupling reaction
Coupling reaction
A coupling reaction in organic chemistry is a catch-all term for a variety of reactions where two hydrocarbon fragments are coupled with the aid of a metal catalyst...

s including the Suzuki reaction
Suzuki reaction
The Suzuki reaction is the organic reaction of an aryl- or vinyl-boronic acid with an aryl- or vinyl-halide catalyzed by a palladium complex. It is widely used to synthesize poly-olefins, styrenes, and substituted biphenyls, and has been extended to incorporate alkyl bromides...

 and the Ullmann reaction
Ullmann reaction
The Ullmann reaction or Ullmann coupling is a coupling reaction between aryl halides with copper. The reaction is named after Fritz Ullmann....

 and have many uses. Polychlorinated biphenyl
Polychlorinated biphenyl
Polychlorinated biphenyls are a class of organic compounds with 2 to 10 chlorine atoms attached to biphenyl, which is a molecule composed of two benzene rings. The chemical formula for PCBs is C12H10-xClx...

s were once used as cooling and insulating fluids and polybrominated biphenyl
Polybrominated biphenyl
Polybrominated biphenyls , also called brominated biphenyls or polybromobiphenyls, are a group of manufactured chemicals, of the polyhalogenated compounds. Their chlorine analogs are the PCBs...

s are flame retardant
Flame retardant
Flame retardants are chemicals used in thermoplastics, thermosets, textiles and coatings that inhibit or resist the spread of fire. These can be separated into several different classes of chemicals:...

s. The biphenyl motif also appears in drug
Drug
A drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...

s such as valsartan
Valsartan
Valsartan is an angiotensin II receptor antagonist , with particularly high affinity for the type I angiotensin receptor. By blocking the action of angiotensin, valsartan dilates blood vessels and reduces blood pressure...

 and telmisartan
Telmisartan
Telmisartan is an angiotensin II receptor antagonist used in the management of hypertension. It is marketed under the trade name Micardis , among others.-Administration:...

. The abbreviation E7 stands for a liquid crystal
Liquid crystal
Liquid crystals are a state of matter that have properties between those of a conventional liquid and those of a solid crystal. For instance, an LC may flow like a liquid, but its molecules may be oriented in a crystal-like way. There are many different types of LC phases, which can be...

 mixture consisting of several cyanobiphenyls with long aliphatic tails used commercially in liquid crystal display
Liquid crystal display
A liquid crystal display is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals . LCs do not emit light directly....

s. A variety of benzidine
Benzidine
Benzidine, the trivial name for 4,4'-diaminobiphenyl, is the solid organic compound with the formula 2. This aromatic amine is a component of a test for cyanide and also in the production of dyes...

 derivatives are used in dyes and polymers. Research into biphenyl liquid crystal candidates mainly focuses on molecules with highly polar heads (for example cyano or halide groups) and aliphatic tails.

See also

  • Triphenyl
  • Terpyridine
    Terpyridine
    Terpyridine is a heterocyclic compound derived from pyridine. This colourless solid is used as a ligand in coordination chemistry.-Synthesis:...

  • Terthiophene
    Terthiophene
    Terthiophene is the organic compound with the formula [C4H3S]2C4H2S. It is an oligomer of the heterocycle thiophene, a shorter oligomer is dithienyl, and the parent polymer is polythiophene...

  • Naphthalene
    Naphthalene
    Naphthalene is an organic compound with formula . It is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromatic hydrocarbon, naphthalene's structure consists of a fused pair of benzene rings...

     where the rings are fused.
  • Tricyclobutabenzene
    Tricyclobutabenzene
    Tricyclobutabenzene is an aromatic hydrocarbon consisting of a benzene core with three cyclobutane rings fused onto it. This compound and related compounds are studied in the laboratory because they are often display unusual conformations and because of their unusual reactivity...

    contains two more hydrogen atoms than biphenyl

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK