Biphenyl
- Diphenyl
- Phenylbenzene
- Dibenzene
Colorless, aromatic odor Papers
Fixed
1.04 g · cm -3
69.2 ° C
255 ° C
7 Pa ( 20 ° C)
- Insoluble in water
- Soluble in ethanol and diethyl ether
1.588 (77 ° C)
Attention
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Biphenyl ( also biphenyl, phenylbenzene and dibenzene ) is a colorless crystalline solid from the class of aromatic hydrocarbons, specifically, the biaryl. It inhibits the growth of mold and therefore acts as a fungicide or a food preservative, but has no authorization in the EU.
Properties
Physical Properties
Biphenyl forms colorless to yellowish shiny crystals which melt at 69.2 ° C. The enthalpy of fusion 18.576 kJ · mol -1. The boiling point at atmospheric pressure is 255 ° C. The enthalpy of vaporization is 47.95 kJ · mol at the boiling point -1. The vapor pressure function is given by Antoine corresponding log10 (P) = A- ( B / ( T C )) ( P in bar, T in K) with A = 4.35685, B = 1987.623 and C = -71.556 in temperature range from 342 K to 544 K. biphenyl is insoluble in water, in nonpolar organic solvents such as petroleum ether or toluene, however, it dissolves easily. The flash point is 113 ° C, the ignition temperature at 540 ° C.
Chemical Properties
Biphenyl is relatively inert. The hydrogenation over platinum catalysts via the cyclohexyl benzene to cyclohexylcyclohexane.
Use and preparation
Biphenyl was in the past as a preservative ( food additive E230, often in combination with E 231, E 232, E 233 and imazalil ) applied to the peel of citrus fruits, because it inhibits the growth of molds. The shells are treated in such a way, however, no longer suitable for consumption. The active ingredient biphenyl (formerly diphenyl ) has been deleted in the EU from the list of permissible surface treatment agent in 2005.
Because of its effects, it can also be used as a pesticide, but such use is not permitted in the EU ( not included in Annex I to Directive EU 91/414 ). Biphenyl also required for the production of pharmaceutical products, and polychlorinated biphenyls.
Biphenyl is the base for the first commercially successful nematic liquid crystals ( cyanobiphenyls ) who came in digital watches and calculators beginning of the 1970s for use.
Because of the high decomposition temperature under exclusion of air to biphenyl suitable as a heat carrier and as a working medium in steam power plants.
Biphenyl is obtained from the distilled oils of Steinkohleteers.
Hazards
Biphenyl is irritating to the skin, eyes and respiratory tract and is dangerous for the environment. Biphenyl is hazardous to water ( WGK 2) and is suspected to cause cancer.