Biphenyl and Terphenyls

Abstract

Biphenyl (diphenyl, phenylbenzene) and terphenyl are the lowest members of a family of polyphenyls in which benzene rings are attached one to another in a chainlike manner, C 6 H 5 (C 6 H 4 ) m C 6 H 5 . Many higher polyphenyls are known, but only biphenyl and the terphenyls are of commercial significance. Pure biphenyl is a white crystalline solid that separates from solvents as plates or monoclinic prismatic crystals. Commercial samples are often slightly yellow or tan in color. Similarly, pure terphenyls are white crystalline solids whereas commercial grades are somewhat yellow or tan. Biphenyl and terphenyls may be regarded as substituted benzenes that undergo acylation, alkylation, halogenation, nitration, sulfonation, and other reactions common to benzene. Terphenyls, like biphenyl, undergo the usual reactions of aromatic hydrocarbons. Biphenyl is recovered from high boiler fractions that accompany the hydrodealkylation of toluene to benzene. High purity biphenyl is produced by Monsanto by direct dehydro‐condensation of benzene. Terphenyls are also obtained from the higher boiling polyphenyl by‐products that accompany the biphenyl. By‐product biphenyl is usually sold as a dye carrier in the molten state in tank truck or tank car lots. Grades of higher purity are also sold in the molten state or as flakes in 22.7‐kg bags. Biphenyl is defined as a toxic chemical under, and subject to, reporting requirements of Section 313 of Title III of the Superfund Amendments and Reauthorization Act (SARA) of 1986 and 40 CFR, Part 372, under the name biphenyl. It is identified as a hazardous chemical under criteria of the OSHA Hazard Communication Standard (29 CFR 1910.1200). The small amount of mixed terphenyls that are sold as such are shipped in the form of flaked solids in 22.7‐kg multiwall bags. Like biphenyl, mixed terphenyls fall under the hazardous chemical criteria of the OSHA Hazard Communication Standard (29 CFR 1910.1200). About 10% of the biphenyl derived from HDA sources is consumed as 93–95% grade in textile dye carrier applications. The remainder is used for alkylation or upgraded to grades for heat‐transfer purposes. Most of the terphenyl produced is converted to a partially hydrogenated form. Although biphenyl and the terphenyls fall under the hazardous chemical criteria of the OSHA Hazard Communications Standard, the products themselves are fairly low in toxicity and do not constitute a serious industrial hazard. Because biphenyl is often transported in the molten state, a moderate fire hazard does exist. The widespread use of biphenyl and methyl‐substituted biphenyls as dye carriers in the textile industry has given rise to significant environmental concern because of the amount released to the environment in wastewater effluent. The prospect of their conversion by chlorination to PCBs in the course of wastewater treatment has been a subject of environmental focus. Terphenyls do not constitute an environmental threat. Short‐chain alkylated biphenyls are the principal biphenyl derivatives in commercial use. Several functionalized biphenyls either are, or show promise of becoming, commercially significant polymer building blocks.

Benzylation of Biphenyl with Benzyl Chloride over Amorphous Silica−Alumina: A Kinetic Study

“…Although polychlorinated biphenyls (PCB) had to be discarded for environmental reasons, there is interest for biphenyl and its derivatives because of their high boiling point, thermal stability, and physicochemical properties. Some of them are useful in heat-transfer and other applications, for instance, as dye solvents , …”

Pd-Catalyzed Aerobic Oxidative Coupling of Arenes: Evidence for Transmetalation between Two Pd(II)-Aryl Intermediates

“…Prominent targets include the conversion of methane to higher hydrocarbons and the coupling of arenes to biaryls. The latter application is relevant to the industrial production of heat transfer fluids (e.g., biphenyl) and monomers for high-performance polymers (e.g., Upilex). Moreover, oxidative cross-coupling of arenes represents an efficient route to unsymmetrical biaryls relevant to the pharmaceutical, agrochemical, and fine chemical industries .…”

Comparison of three stationary phases in the separation of polyphenyls by liquid chromatography

“…Higher phenyls, and their derivatives, are currently being used as precursors for graphene synthesis [1] organic liquid crystals, [2,3] organic LEDs, [4,5] and polymers, [6,7] while their largest application, by volume, is as heat transfer fluids (HTFs). [8] Industrially, the production of biphenyl, terphenyls and quaterphenyls is carried out by the pyrolysis of benzene. [8] The pyrolysis product was studied in the 1950s as a coolant for nuclear reactors and has since formed the basis of a number of HTFs.…”

“…[8] Industrially, the production of biphenyl, terphenyls and quaterphenyls is carried out by the pyrolysis of benzene. [8] The pyrolysis product was studied in the 1950s as a coolant for nuclear reactors and has since formed the basis of a number of HTFs. [9] Organic based, and in particular aromatic, fluids are attractive as they present a lower pressure alternative to water/steam-based cooling systems, are less corrosive and exhibit high stability.…”