2,2 -Dihydroxybiphenyls

Thermotropic polycarbonates have been prepared from mixtures of 4,4 -dihydroxybiphenyl and various diphenols (10). Nematic melts were found for copolycarbonates prepared from methyfliydroquiaone, chlorohydroquiaone, 4,4 -dihydroxydiphenyl ether, and 4,4 -dihydroxybenzophenone. Slightly crystalline polycarbonates have been prepared from mixtures of hydroquinone and BPA (T = 154°C, =313°C, AH = 11.0 J/g (2.63 cal/g)), and... 

Chlorinated dibenzo ip-dioxins are contaminants of phenol-based pesticides and may enter the environment where they are subject to the action of sunlight. Rate measurements showed that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is more rapidly photolyzed in methanol than octachlorodi-benzo-p-dioxin. Initially TCDD yields 2,3,7-trichlorodiben-zo-p-dioxin, and subsequent reductive dechlorination is accompanied by ring fission. Pure dibenzo-p-dioxin gave polymeric material and some 2,2 -dihydroxybiphenyl on irradiation. Riboflavin-sensitized photolysis of the potential precursors of dioxins, 2,4-dichlorophenol and 2,4,5-trichloro-phenol, in water gave no detectable dioxins. The products identified were chlorinated phenoxyphenols and dihydroxy-biphenyls. In contrast, aqueous alkaline solutions of purified pentachlorophenol gave traces of octachlorodibenzo-p-dioxin on irradiation. 

Up to now, nine classes of different polyphosphazenes are known and characterized substituted with aliphatic alcohols [40,41,262-281] or phenols [41,95, 277,282-297],with aliphatic [42,298-300] or aromatic [301-304] amino groups, with di-functional spiro hydroxy (e.g. dihydroxybiphenyl [305] or di hydroxy-... 

The phosphazene backbone has a particularly high resistance to thermal treatment and to homolytic scission of the -P=N- bonds, possibly due to the combination of the high strength of the phosphazene bond and its remarkable ionic character [456]. As a consequence, the onset of thermal decomposition phenomena (as detected, for instance, by TGA) are observed at considerably high temperatures for poly[bis(trifluoroethoxy)phosphazene], [NP(OCH2CF3)2]n [391, 399, 457], for phosphazene copolymers substituted with fluorinated alcohols of different length [391, 399, 457], for polyspirophosphazenes substituted with 2,2 -dihydroxybiphenyl groups [458], and for poly(alkyl/aryl)-phosphazenes [332]. 

Other polymers have been reported from the reactions of N3P3CI6 with alkoxyboron compounds, the sodium salt of hydroquinone, and 4,4 -dihydroxybiphenyl. ... 

Whereas photolysis of 2- and 4-chlorophenols in aqueous solution produced catechol and hydroquinone, in ice the more toxic dimeric chlorinated dihydroxybiphenyls were formed (Blaha et al. 2004). 

Asturias JA, KN Timmis (1993) Three different 2,3-dihydroxybiphenyl-l, 2-dioxygenase genes in the Gram-positive polychlorobiphenyl-degrading bacterium Rhodococcus globerulus P6. J Bacteriol 175 4631-4640. 

Hatta T, G Mukleijee-Dhar, J Damborsky, H Kiyohara (2003) Characterization of a novel thermostable Mn(ll)-dependent 2,3-dihydroxybiphenyl 1,2-dioxygenase from polychlorinated biphenyl- and naphthalene-degrading Bacillus sp. JE8. J Biol Chem 278 21483-21492. 

C subfamily of type 1 extradiol dioxygenases (Mars et al. 1999). The alternative extradiol fission of 3-chlorocatechol may take place between the 1 and 6 positions (distal fission), and this has been shown for the 2,3-dihydroxybiphenyl 1,2-dioxygenase from the naphthalene sulfonate degrading Sphingomonas sp. strain BN6 (Riegert et al. 1998). 

Furukawa K, N Arimura (1987) Purification and properties of 2,3-dihydroxybiphenyl dioxygenase from polychlorinated biphenyl-degrading Pseudomonas pseudoalcaligenes and Pseudomonas aeruginosa carrying the cloned bphC gene. J Bacterial 169 924-927. 

Lloyd-Jones G, RC Ogden, PA Williams (1995) Inactivation of 2,3-dihydroxybiphenyl 1,2-dioxygenase from Pseudomonas sp. strain CB406 by 3,4-dihydroxybiphenyl (4-phenyl catechol). Biodegradation 6 11-17. 

Khan AA, R-F Wang, MS Nawaz, W-W Cao, CC Cerniglia (1996) Purification of 2,3-dihydroxybiphenyl 1,2-dioxygenase from Pseudomonas putida OU83 and characterization of the gene (bphC). Appl Environ Microbiol 62 1825-1830. 

The hrst enzyme in the degradation of 2-hydroxybiphenyl by Pseudomonas azelaica strain HBPl is an FAD-dependent monooxygenase that produces 2,3-dihydroxybiphenyl (Suske et al. 1999). 

Asturias lA, LD Eltis, M Prucha, KN Timmis (1994) Analysis of three 2,3 -dihydroxybiphenyl 1,2-dioxygenases found in Rhodococcus globerulus P6. J Biol Chem 269 7807-7815. 

Degradation of PCBs is carried out by a suite of enzymes comprising biphenyl-2,3-dioxygenase, biphenyl-2,3-dihydrodiol dehydrogenase, 2,3-dihydroxybiphenyl dioxygenase, and the hydrolytic enzymes that produce benzoate encoded by the genes bphA, bphB, bphC, and bphD (Furukawa and Miyazaki 1986 Ahmad et al. 1991 Taira et al. 1992). 

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