Biphenyl chemical structure

PCDFs are similar in many respects to PCDDs but have been less well studied, and will be mentioned only briefly here. Their chemical structure is shown in Figure 7.1. Like PCDDs, they can be formed by the interaction of chlorophenols, and are found in commercial preparations of chlorinated phenols and in products derived from phenols (e.g., 2,4,5-T and related phenoxyalkanoic herbicides). They are also present in commercial polychlorinated biphenyl (PCB) mixtures, and can be formed... 

Fig. 7 Generic chemical structures of polyhalogenated compounds. X=C1, Br. (I) Polychlorinated biphenyls (PCBs), polybrominated biphenyls (PBBs) (II) chlorophenols (CPs), bromophenols (BPs) (III) polychlorinated diphenyl ethers (PCDE), polybrominated diphenyl ethers (PBDE) (IV) polychlorinated dibenzo-p-dioxin (PCDD), polybrominated dibenzo-p-dioxin (PBDD) (V) polychlorinated dibenzofuran (PCDF), polybrominated dibenzofuran (PBDF) (VI) tetrabromobisphenol A (TBBPA)...

Careful 1H and 13C NMR analyses were carried out for both monomers and polymers in order to prove the chemical structures of the polymers. The H NMR spectra of 50 and 52 are shown in Figure 8. As polymerization proceeded, an acetylenic proton peak at 2.0-2.2 ppm disappeared, while a new vinylic proton peak appeared broadly in the 6.8-7.2 ppm range. Since the new peak is weaker than those for the aromatic biphenyl rings and the two peaks are superimposed, it is hard to separate them clearly. The broad peaks at 2.6 and 3.4 ppm are assignable to the methylene protons and methine proton in the ring, respectively. 

Principally, one commercially available sulfonated diamine (4,4 -diamino-2,2 -biphenyl disulfonic acid) has been used to synthesize sulfonated polyimides. In addition to the commercially available diamine, several novel sulfonated diamines incorporating flexible or kinked structures have been prepared in Okamoto s lab. " The chemical structures and names of all five diamines are shown in Figure 23. 

The role of size exclusion chromatography is the separation of rather complex coal liquids into simpler fractions. The retention volume can be used to help Identify the chemical structure where GC-MS is unable to identify its possible structure. For example biphenyl and dihydroacenaphthene have the same molecular formula as well as similar mass spectral fragmentation patterns. Coal liquids contain both species. The one which appears first (lower SEC retention volume) is biphenyl (GC ret. time = 17 min. in Figure 5-6). Dihydroacenaphthene appears later at longer SEC retention volume and is identified in Figure 5-12 at GC retention time of 13 minutes. The former has a longer structure compared to the latter. 

Polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers (PBDEs) are each classes of structurally similar brominated hydrocarbons. PBBs are a class of chemical compounds in which 2 10 bromine atoms are attached to the biphenyl molecule. PBDEs are a class of chemical confounds in which 2 10 bromine atoms are attached to the diphenyl ether molecule. Monobrominated structures (i.e., one bromine atom attached to the molecule) are often included when describing PBBs and PBDEs. The general chemical structures of PBBs and PBDEs are similar when viewed in one dimension, differing only in an ether linkage, as shown below ... 

Biphenyl and aromatic ester series of ferroelectric liquid crystals Numerous 4-alkoxy (or 4-alkyl) biphenyl-4 -carboxylate compounds were synthesized. The basic chemical structure of these is presented in Figure 40. These compounds show ferroelectric phases at room temperature, but their spontaneous polarizations are relatively small. 

Fig. 10.3 Chemical structures of low affinity NMDA antagonists used for the treatment of AD, AD, AIDS dementia, and migrane. Memantine (a) Amantadine (b) (R,S)-N-2-(4-(3-thienyl)phenyl)-2-propanesulfonamide (LY392098) (c) and (R)-4 -[l-fluoro-l-methyl-2-(propane-2-sulphonylamino)-ethyl]-biphenyl-4-carboxylic acid methylamide (LY503430) (d)...

Fig-1 Chemical structures of polychlorinated naphthalene (PCN), polychlorinated biphenyl (PCB), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)... 

Figure 3.25 Chemical structure of N.N1 -bis(4-tert-butylphenyl)WW-bis(4-(( )-2-(triethoxysilyl)vinyl)phenyl)biphenyl-4,4 -diamine (BBDA).

Next, just as the synergy between nomenclature and chemical structure was illustrated for biphenyl vs. biphenylene, attention is directed to a newly discovered compound having a bent sp-hybridized skeleton [26], Due to the postulation of the bet bond (Chapter 2), the proposed systemic nomenclature for the trisilaallene molecule does not convey the false picture... 

Fig. 4 Chemical structures of monomers with biphenyl mesogens...

It is very likely that the polybrominated biphenyls are metabohzed in fish, sea mammals, and human to debrominated and hydroxylated polybrominated biphenyls. It is suggested by the authors that some of these polybrominated metabolites can bind to the estrogen receptor and act hke xenoestrogens, as was shown for hydroxy polychlorinated biphenyls (HO-PCBs) by Korach et al. [256], McKinney and Waller [257], and Waller et al. [258]. Especially the chemical structure of para-substituted hydroxylated metabohtes of polybrominated biphenyls would be similar to that of estradiol, preferably in the presence of... 

Table 15. Chemical name, trade name, CAS No., chemical structure, molecular formula, molecular weight, n-octanol/water partition coefficient (Kqw), bioconcentration factors on a lipid basis (BCFl) in fish, and residues found in environmental samples (sediments, mussels, fish) and human fat of Polybrominated Benzenes (PBBzs), Polybrominated Biphenyls (PBBs), and Polybrominated Diphenylethers (PBDEs)... 

Fig. 7.25 Chemical structures of the contrasting persistent organic pollutants (POPs), polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and furans (PCDDs/PCDFs), p,p -dichlorodiphenyl trichloroethane (DDT) and hexachlorocyclohexane (HCH). Symbols x and y indicate the possible number of chlorines attached to the ring structures.

PCBs are a class of chemical compounds in which 2-10 chlorine atoms are attached to the biphenyl molecule. Monochloiinated biphenyls (i.e., one chlorine atom attached to the biphenyl molecule) are often included when describing PCBs. The general chemical structure of chlorinated biphenyls is shown below. 

Chemical decontamination is an alternative to thermal processing or landfilling of soils contaminated with polychlorinated dibenzo-p- dioxins (PCDD) or other aromatic halides such as chlorobenzenes or polychorinated biphenyls (PCB). Chemical decontamination, like incineration, involves changes to the chemical structure of the dioxin molecule. While chlorinated dioxins are thermally stable, they readily dechlorinate to water soluble compounds under relatively mild conditions of temperature and pressure. 

Figure 1 Chemical structures of (A) polychlorinated biphenyls (PCBs) (B) dichlorodiphenyltrichloroethane (DDT) and the metabolites dichlorophenyidichloroethane (DDD) and DDE (C) other chlorinated pesticides. C, carbon atoms H, hydrogen atom Cl, chlorine atom.

The radical anion derived from 2-cyanodiphenyl ether underwent reversible dimerization resulting in a dianion relatively resistant towards further chemical reaction. The products observed after electrolysis were mainly phenol, diphenyl ether and 2, 4-dicyano-3-phenoxy biphenyl. The structure of the isolated biphenyl suggested that the radical anion dimerization had occurred via 2-4 coupling. 

Fig. 5.18. Absorption spectra, chemical structure, and proposed energy band levels of the materials used in the bi-layer hetero junction photoconductor N, N -bis(3-methylphenyl)-W,W -diphenyl-l,l/-biphenyl-4,4 -diamine (TPD, solid) and 3,4,9,10-perylenetetracarboxylic bis-benzimidazole (PTCBI, dashes). Also shown is the emission profile of the green LED (green, Apeak 532 nm) operated with a forward current of 2 A and an intensity of approximately 40 mW cnT (dotted)...

Although chemical structures do not play a role in the lubrication, Shiff bases, azoxys and cyano biphenyls discompose under tropical conditions and cannot be used. 

Among the major ubiquitous SVOC pollutants in the urban air worldwide are polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). Their chemical structures are presented in Figs. 1, 2. Theoretically, there are 57 individual PAHs which contain 2-6 fused six-member benzenoid rings only (Harvey 1997). There are 209 individual PCB congeners and 209 individual PBDE congeners, varying in the number and positions of the substitutions by chlorine and bromine, respectively. 

FIGURE 7.1 Chemical structures of the main-chain LCs treated in this chapter, nCB being included for comparison. Phase-transition temperatures (DSC) are given to the individual formulas. Note that o, [Pg.286]

Chart 6.10 Chemical structures of 4,4 -di(/ /-carbazolyl)-biphenyl, CBP, and 2- 4-biphenyl)-5-(4-tert-butylphenyl)-l, 3,4-oxadiazole, PBD. 

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