Chemistry:Biphenyl

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Biphenyl
Skeletal formula
Space filling model showing its twisted conformation
sample
Names
Preferred IUPAC name
1,1′-Biphenyl
Other names
Biphenyl
Phenylbenzene
Dibenzene
Xenene
Identifiers
3D model (JSmol)
3DMet
1634058
ChEBI
ChEMBL
ChemSpider
EC Number
  • 202-163-5
3808
KEGG
RTECS number
  • DU8050000
UNII
UN number 3077
Properties
C12H10
Molar mass 154.212 g·mol−1
Appearance Colorless to pale-yellow crystals
Odor pleasant[1]
Density 1.04 g/cm3[2]
Melting point 69.2 °C (156.6 °F; 342.3 K)[2]
Boiling point 255 °C (491 °F; 528 K)[2]
4.45 mg/L[2]
Vapor pressure 0.005 mmHg (20°C)[1]
−103.25·10−6 cm3/mol
Hazards
GHS pictograms GHS07: HarmfulGHS09: Environmental hazard
GHS Signal word Warning
H315, H319, H335, H410
P261, P264, P271, P273, P280, P302+352, P304+340, P305+351+338, P312, P321, P332+313, P337+313, P362, P391, P403+233, P405, P501
NFPA 704 (fire diamond)
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilHealth code 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
1
1
0
Flash point 113 °C (235 °F; 386 K)[2]
540 °C (1,004 °F; 813 K)[2]
Explosive limits 0.6–5.8%[1]
Lethal dose or concentration (LD, LC):
2400 mg/kg (oral, rabbit)
3280 mg/kg (oral, rat)
1900 mg/kg (oral, mouse)
2400 mg/kg (oral, rat)[3]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 1 mg/m3 (0.2 ppm)[1]
REL (Recommended)
 TWA 1 mg/m3 (0.2 ppm)[1]
IDLH (Immediate danger)
 100 mg/m3[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is ☑Y☒N ?)
Infobox references
Tracking categories (test):

Biphenyl (also known as diphenyl, phenylbenzene, 1,1′-biphenyl, lemonene[4] or BP) is an organic compound that forms colorless crystals. Particularly in older literature, compounds containing the functional group consisting of biphenyl less one hydrogen (the site at which it is attached) may use the prefixes xenyl or diphenylyl.[5]

It has a distinctively pleasant smell. Biphenyl is an aromatic hydrocarbon with a molecular formula (C6H5)2. It is notable as a starting material for the production of polychlorinated biphenyls (PCBs), which were once widely used as dielectric fluids and heat transfer agents.

Biphenyl is also an intermediate for the production of a host of other organic compounds such as emulsifiers, optical brighteners, crop protection products, and plastics. Biphenyl is insoluble in water, but soluble in typical organic solvents. The biphenyl molecule consists of two connected phenyl rings.

Properties and occurrence

Biphenyl is a solid at room temperature, with a melting point of 69.2 °C (156.6 °F). In the gas phase the molecule exists in two enantiomorphic twisted forms with an angle between the planes of the two rings of 44.4°. In the room-temperature solid, biphenyl is crystalline with space group P21/c, which does not allow for chiral crystals. Rather than there being a double-well potential entailing the two twisted conformations, the potential energy is minimized at zero twist.[6][7]

Biphenyl occurs naturally in coal tar, crude oil, and natural gas and can be isolated from these sources via distillation.[8] It is produced industrially as a byproduct of the dealkylation of toluene to produce methane:

C
6H
5CH
3 + C
6H
6 → C
6H
5–C
6H
5 + CH
4

The other principal route is by the oxidative dehydrogenation of benzene:

2 C
6H
6 + 1/
2 O
2 → C
6H
5–C
6H
5 + H
2O

Annually 40,000,000 kg are produced by these routes.[9]

In the laboratory, biphenyl can also be synthesized by treating phenylmagnesium bromide with copper(II) salts.

It can also be prepared using diazonium salts. When aniline is treated with NaNO2+dilute HCl at 5°C, it yields benzene diazonium chloride. When this is further reacted with benzene, biphenyl is formed. This is known as the Gomberg–Bachmann reaction.

[math]\ce{ Ph-NH2->[\text{NaNO}_2\text{(aq), HCl}][T\text{=273-278K}] Ph-N2+ ->[\text{Ph-H, Δ}] Ph-Ph }[/math]

Reactions and uses

Lacking functional groups, biphenyl is fairly non-reactive, which is the basis of its main application: its use as a heat transfer agent as a eutectic mixture with diphenyl ether. This mixture is stable to 400 °C.[9]

Biphenyl does undergo sulfonation which, followed by base hydrolysis, produces p-hydroxybiphenyl and p,p′-dihydroxybiphenyl, which are useful fungicides. In other substitution reactions, it undergoes halogenation. Polychlorinated biphenyls were once popular pesticides.[9]

Li biphenyl radical

Lithium biphenyl contains the radical anion, which is highly reducing (-3.1 V vs Fc+/0). Several solvates of alkali metal salts of biphenyl anion have been characterized by X-ray crystallography.[10] These salts, usually prepared in situ, are versatile reducing agents.[11] Lithium biphenyl offers some advantages relative to the related lithium naphthene.[12] Related to Li/biphenyl is the derivative with tert-butyl groups on the biphenyl.[13]

Stereochemistry

Rotation about the single bond in biphenyl, and especially its ortho-substituted derivatives, is sterically hindered. For this reason, some substituted biphenyls show atropisomerism; that is, the individual C2-symmetric-isomers are optically stable. Some derivatives, as well as related molecules such as BINAP, find application as ligands 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°.[14] 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).[15]

Biphenyl compounds

Substituted biphenyls have many uses. They are prepared by various coupling reactions including the Suzuki-Miyaura reaction and the Ullmann reaction. Polychlorinated biphenyls were once used as cooling and insulating fluids and polybrominated biphenyls are flame retardants. The biphenyl motif also appears in drugs such as diflunisal and telmisartan. The abbreviation E7 stands for a liquid crystal mixture consisting of several cyanobiphenyls with long aliphatic tails used commercially in liquid crystal displays (5CB, 7CB, 8OCB and 5CT[16]). A variety of benzidine 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. It is part of the active group in the antibiotic oritavancin.

Safety and bioactivity

Biphenyl prevents the growth of molds and fungus, and is therefore used as a preservative (E230, in combination with E231, E232 and E233), particularly in the preservation of citrus fruits during transportation. It is no longer approved as a food additive in the European Union.

Biphenyl is mildly toxic, but can be degraded biologically by conversion into nontoxic compounds. Some bacteria are able to hydroxylate biphenyl and its polychlorinated biphenyls (PCBs).[17]

See also

Notes

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 NIOSH Pocket Guide to Chemical Hazards. "#0239". National Institute for Occupational Safety and Health (NIOSH). https://www.cdc.gov/niosh/npg/npgd0239.html. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Record in the GESTIS Substance Database of the Institute for Occupational Safety and Health
  3. ↑ "Diphenyl". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH). 4 December 2014. https://www.cdc.gov/niosh/idlh/92524.html. 
  4. ↑ "Biphenyl". US National Institute of Standards and Technology. https://webbook.nist.gov/cgi/cbook.cgi?ID=92-52-4.  An obscure name, according to "Limonene". American Chemical Society. Nov 1, 2021. https://www.acs.org/molecule-of-the-week/archive/l/limonene.html. 
  5. ↑ "Beilsteins Handbuch der organischen Chemie, Volume 5". https://archive.org/stream/beilsteinshandb01gesegoog/beilsteinshandb01gesegoog_djvu.txt. 
  6. ↑ Dr. Bruno Landeros-Rivera, Jesús Hernández-Trujillo (Dec 15, 2021). "Control of Molecular Conformation and Crystal Packing of Biphenyl Derivatives". Chemistry Europe. doi:10.1002/cplu.202100492. https://chemistry-europe.onlinelibrary.wiley.com/doi/epdf/10.1002/cplu.202100492. 
  7. ↑ Bruno Landeros-Rivera, Vojtech Jancik, Rafael Moreno-Esparza, Diego Martínez Otero, Jesús Hernández-Trujillo (May 27, 2021). "Non-Covalent Interactions in the Biphenyl Crystal: Is the Planar Conformer a Transition State?". Chemistry Europe. doi:10.1002/chem.202101490. 
  8. ↑ Adams, N. G., and D. M. Richardson, 1953. Isolation and Identification of Biphenyls from West Edmond Crude Oil. Analytical Chemistry 25 (7): 1073-1074
  9. ↑ 9.0 9.1 9.2 Karl Griesbaum, Arno Behr, Dieter Biedenkapp, Heinz-Werner Voges, Dorothea Garbe, Christian Paetz, Gerd Collin, Dieter Mayer, Hartmut Höke "Hydrocarbons" in Ullmann's Encyclopedia of Industrial Chemistry 2002 Wiley-VCH, Weinheim. doi:10.1002/14356007.a13_227
  10. ↑ Castillo, Maximiliano; Metta-Magaña, Alejandro J.; Fortier, Skye (2016). "Isolation of gravimetrically quantifiable alkali metal arenides using 18-crown-6". New Journal of Chemistry 40 (3): 1923–1926. doi:10.1039/C5NJ02841H. 
  11. ↑ Yanagisawa, Akira; Yasue, Katsutaka; Yamamoto, Hisashi (1997). "Regio- and Stereoselective Carboxylation of Allylic Barium Reagents: (E)-4,8-dimethyl-3,7-nonadienoic Acid". Org. Synth. 74: 178. doi:10.15227/orgsyn.074.0178. 
  12. ↑ Rieke, Reuben D.; Wu, Tse-Chong; Rieke, Loretta I. (1995). "Highly Reactive Calcium for the Preparation of Organocalcium Reagents: 1-Adamantyl Calcium Halides and Their Addition to Ketones: 1-(1-Adamantyl)cyclohexanol". Org. Synth. 72: 147. doi:10.15227/orgsyn.072.0147. 
  13. ↑ Mudryk, Boguslaw; Cohen, Theodore (1995). "1,3-Diols from Lithium β-Lithioalkoxides Generated by The Reductive Lithiation of Epoxides: 2,5-Dimethyl-2,4-hexanediol". Org. Synth. 72: 173. doi:10.15227/orgsyn.072.0173. 
  14. ↑ Mikael P. Johansson and Jeppe Olsen (2008). "Torsional Barriers and Equilibrium Angle of Biphenyl: Reconciling Theory with Experiment". J. Chem. Theory Comput. 4 (9): 1460–1471. doi:10.1021/ct800182e. PMID 26621432. 
  15. ↑ B. Testa (1982). "The geometry of molecules: basic principles and nomenclatures". in Christoph Tamm. Stereochemistry. Elsevier. pp. 18. 
  16. ↑ Mouquinho, Ana; Saavedra, Mara; Maiau, Alexandre; Petrova, Krasimira; Barros, M. Teresa; Figueirinhas, J. L.; Sotomayor, João (30 June 2011). "Films Based on New Methacrylate Monomers: Synthesis, Characterisation and Electro-Optical Properties". Molecular Crystals and Liquid Crystals 542 (1): 132/[654]–140/[662]. doi:10.1080/15421406.2011.570154. 
  17. ↑ "Biphenyl degradation - Streptomyces coelicolor, at GenomeNet Database". genome.jp. http://www.genome.jp/dbget-bin/show_pathway?sco00621+SCO6442. 

References

  • "Isolation and Identification of Biphenyls from West Edmond Crude Oil". N. G. Adams and D. M. Richardson. Analytical Chemistry 1953 25 (7), 1073–1074.
  • Biphenyl (1,1-Biphenyl). Wiley/VCH, Weinheim (1991), ISBN:3-527-28277-7.

External links



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