Biphenyl determination

Jimenez, O. Jimenez, B. Gonzalez, M.J., Isomer-specihc polychlorinated biphenyl determination in cetaceans from the Mediterranean Sea Enantioselective occurrence of chiral polychlorinated biphenyl congeners Environ. Toxicol. Chem. 2000, 19, 2653-2660. 

Lilienthal H, Winneke G. 1991. Sensitive periods for behavioral toxicity of polychlorinated biphenyls Determination by cross-fostering in rats. Fundam Appl Toxicol 17 368-375. 

The. more tightly held an electron is. the more difficult it is to remove, hence the higher the electrode potential necessary to remove it. Make the reasonable hypothesis that the electron removed in a one-electron oxidation comes from the highest occupied orbital. HOMO. Using SHMO. determine the HOMO for ben7 ene, biphenyl, and naphthalene. 

Solvent extraction followed by gas chromatographic analysis is used to determine paraffin wax antioxidants (qv), ie, butylated hydroxyanisole and butylated hydroxytoluene and other volatile materials. Trace amounts of chlorinated organic compounds, eg, polychlorinated biphenyls, can be deterrnined by using a gas chromatograph with an electron-capture detector (22). 

Properties have been determined for a series of block copolymers based on poly[3,3-bis(ethoxymethyl)oxetane] and poly [3,3-bis(methoxymethyl)oxetane]- (9-tetrahydrofuran. The block copolymers had properties suggestive of a thermoplastic elastomer (308). POX was a good main chain for a weU-developed smectic Hquid crystalline state when cyano- or fluorine-substituted biphenyls were used as mesogenic groups attached through a four-methylene spacer (309,310). Other side-chain Hquid crystalline polyoxetanes were observed with a spacer-separated azo moiety (311) and with laterally attached mesogenic groups (312). 

SW-846, is used to measure emissions of semivolatile principal organic constituents. Method 0010 is designed to determine destruction and removal efficiency (DRE) of POHCs from incineration systems. The method involves a modification of the EPA Method 5 sampling train and may be used to determine particulate emission rates from stationary sources. The method is applied to semivolatile compounds, including polychlorinated biphenyls (PCBs), chlorinated dibenzodioxins and dibenzofurans, polycyclic organic matter, and other semivolatile organic compounds. 

In general, capillary gas chromatography provides enough resolution for most determinations in environmental analysis. Multidimensional gas chromatography has been applied to environmental analysis mainly to solve separation problems for complex groups of compounds. Important applications of GC-GC can therefore be found in the analysis of organic micropollutants, where compounds such as polychlorinated dibenzodioxins (PCDDs) (10), polychlorinated dibenzofurans (PCDFs) (10) and polychlorinated biphenyls (PCBs) (11-15), on account of their similar properties, present serious separation problems. MDGC has also been used to analyse other pollutants in environmental samples (10, 16, 17). 

The rates of chlorination of benzene, biphenyl, and diphenylmethane by chlorine acetate in 98 % aqueous acetic acid at 25 °C have also been determined and the second-order rate coefficients are 0.00118, 0.0364, and 0.0311, respective-]y209 , 270 jjje varjation in rate with change in water content of the acetic acid was the same as that previously observed209 for toluene, and thus in ca. 75 % aqueous acid the coefficients were 0.00073, 0.027 and 0.0241 however, elsewhere in ref. 209a a 4-fold decrease in rate coefficient for diphenylmethane was claimed to accompany the same increase in water content of the medium. 

The molecules most profitably studied in connection with purely steric isotope effects have been isotopically substituted biphenyl derivatives. Mislow et al. (1964) reported the first more or less clearcut example of this kind in the isotope effect in the configurational inversion of optically active 9,10-dihydro-4,5-dimethylphenanthrene (7), for which an isotopic rate ratio ( d/ h) of 1-17 at 295-2°K in benzene solution was determined. The detailed conformation of the transition state is not certain in this case, as it involves the mutual passage of two methyl groups, and thus it is difficult to compare the experimental results with... 

In some molecules the molecular dipole is simply dominated by a single polar bond. In sufficiently complex molecules there may be several polar bonds of differing strength. In this case the molecular dipole is determined by their relative orientation. Ab initio studies of 2-2 -difluoro biphenyl have revealed a strong shape dependence of the molecular dipole as a function of inter-ring angle. This is illustrated in Fig. 12. 

Hori and Ohashi [162] found three crystal forms for the compound 4 -hexyloxy-4-biphenyl p-[(S)-2-methylbutyl]benzoate. The structures of two crystal forms I-T (triclinic) and II-M (monoclinic) of this compound were determined. The crystal structure of I-T contains four crystallographically independent molecules. The dihedral angles between the phenyl rings of the... 

The IR dichroism measurements allowed a fairly precise determination of the preferential molecular conformations both in the smectic Ai and X phases (see Sect. 2.3). In the smectic Ai phase the biphenyl moiety is parallel on average to the layer normal, while the hydrocarbon and perfluorinated fragments are tilted at angles 18 and 32°, respectively. The phase transition to the smectic X phase is accompanied by a dramatic change in the main molecular conformation - now all the fragments are strongly tilted with respect to the layer normal (especially the biphenyl core which tilts at an angle of around 56°) (Fig. 12). 

Janak K, G Becker, A Colmsjo, C Ostman, M Athanasiadou, K Valters, A Bergman (1998) Methyl sulfonyl polychlorinated biphenyls and 2,2-bis(4-chlorophenyl)-l,l-dichloroethene in gray seal tissues determinated by gas chromatography with electron capture detection and atomic emission detection. Environ Toxicol Chem 17 1046-1055. 

Mondello FJ, MP Turcich, JH Lobos, BD Erickson (1997) Identification and modification of biphenyl dioxygenase sequences that determine the specificity of polychlorinated biphenyl degradation. Appl Environ Microbiol 63 3096-3103. 

---