Biphenyl ether structure

In Figure 13.2, the intensity of the ion at m/z 170 represents a molecular ion of an aromatic compound. The characteristic losses from the molecular ion (M - 1, M - 28, and M - 29) suggest an aromatic aldehyde, phenol, or aryl ether. The molecular formula of Ci2H 0O is suggested by the molecular ion at m/z 170, which can be either a biphenyl ether or a phenylphenol. The simplest test to confirm the structure is to prepare a TMS derivative, even though m/z 11 strongly indicates the diaryl ether. 

Biphenyl structures and a-carbonyl-p-aryl ether structures, which are both assumed to be present in native lignin with a higher abundance than coniferyl alcohol structures (22,23) and both considered to be important leucochromophores, were not observed among die products, presumably because they are not present in spruce lignin as end groups. Both these types of structures are very stable and unlikely to be structurally changed during mild acid hydrolysis (24). 

An X-ray study of vertaline hydrobromide established the structure and absolute stereochemistry of vertaline as shown in 51 (32, 43). The relative stereochemistry at C-l and C-3 in all alkaloids in the group is the same as in the biphenyl alkaloids for example, the biphenyl ether and lactone group are linked to the quinolizidine ring in axial and equatorial configurations, respectively. 

Lagerine was isolated by Ferris et al. from Lagerstroemia indica (17), and methyllagerine was isolated by Hanaoka et al. (42) from L. indica grown in Japan. The structure of lagerine is unique since it was not possible to convert this base to any known Lythraceae alkaloid. The basic skeletons of O-methyllagerine and vertaline are the same since the mass spectra of the two alkaloids are almost identical. The alkaloids differ in the substitution pattern on the biphenyl ether chromophore, a fact which is reflected in the UV spectra. 

Specific Monomers Released by Thioacidolysis of Various Lignin and Non Lignin Substructures. Monomers can be Recovered if the Aromatic Ring of the Parent Structure is not Involved in C-C or Biphenyl Ether Bond... 

A number of other structural types of pesticides are/may be also of carcinogenicity concern. These include the biphenyl ethers, hydrazides, substituted phenylureas and substituted amino-s-triazines as represented by nitrofen (NCI Technical Report No. 26), daminozide (NCI Technical Report No. 83), monuron (NTP Technical Report No. 266) and propazine (see ref. 29),... 

Lagerine, a biphenyl ether alkaloid of Lagerstroemia indica, was assigned structure... 

Over the last seventy years over sixty species of Aristolochia have been exploited for chemical examination by research groups throughout the world and a variety of compounds have been isolated. The spectrum of physiologically-active metabolites from Aristolochia species covers 14 major groups based on structure aristolochic acid derivatives, aporphines, amides, benzylisoquinolines, isoquinolones, chlorophylls, terpenoids, lignans, biphenyl ethers, flavonoids, tetralones, benzenoids, steroids, and miscellaneous. The aristolochic acid derivatives, host of phenanthrene derived metabolites were further classified into aristolochic acids, sodium salts of aristolochic acids, aristolochic acid alkyl esters, sesqui- and diterpenoid esters of aristolochic acids, aristolactams, denitroaristolochic acids, and aristolactones. The terpenoids can further be subdivided into 4 groups mono-, sesqui-, di- and tetraterpenoids. 

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. 

A different structural modification, which is mainly based on lowering the chain stiffness and as a result also on reducing the intermolecular interactions, is the incorporation of kinked and double kinked comonomers (Fig. 2b and c). Typical monomers with kinks are meta-substituted phenylene derivatives or 4,4 -functionalized biphenyl-ethers and 4,4 -functionalized biphenyl-sulfides. Monomers with double kinks are,... 

In this chapter, two general synthetic methods of poly (aryl ether ketone) copolymers were introduced, that is, (1) nucleophilic substitution step copolycondensation of at least two different monomers of bisphenol and at least one dihalobenzoid compound or at least one monomer of bisphenol and at least two different dihalobenzoid compounds (2) electrophilic Friedel-Crafts copolycondensation of at least two different monomer of diphenyl ether and terephthaloyl chloride or at least one monomer of diphenyl ether and terephthaloyl chloride as well as isophthaloyl chloride. Some representative monomers were included. By the method (1), the synthesis and characterization of structural poly (aryl ether ketone) copolymers—poly (ether ether ketone)-poly (ether ether ketone ketone) (PEEK-PEEKK), poly (ether ether ketone)-poly (ether biphenyl ether ketone) (PEEK-PEDEK), poly (ether ether ketone ketone)-poly (ether biphenyl ether ketone ketone) (PEEKK-PEDEKK), poly (ether ether ketone)-poly (ether ether ketone biphenyl ketone) (PEEK-PEEKDK) and poly (ether biphenyl ether ketone)-poly (ether biphenyl ether ketone biphenyl ketone) (PEDEK-PEDEKDK) were discussed. The s5mthesis and characterization of the functional PAEK copolymers, such as liquid crystal poly (aryl ether ketone) copol5oners, poly (aryl ether ketone) copolymers with pendent group of low dielectric constant and poly (aryl ether ketone) copolymers with crosslinking moieties were also discussed in details. These PAEK copolymers showed a lot of special performance and can maybe be applied in optical waveguides, microelectronics, display devices, membrane materials and so on. 

The structural range of industrially important representatives of these groups is enormous, and includes chlorobenzenes (solvents), polychlorinated biphenyls (PCBs) (hydraulic and insulating fluids), and polybrominated biphenyls and diphenyl ethers (flame retardants). There is widespread concern over both the persistence and the potential toxicity of all these compounds, and sites that have become contaminated during their production represent a threat both to the environment and to human health. Pathways for the aerobic bacterial degradation of chlorobenzenes and chlorobiphe-nyls, and their brominated analogs have been discussed in Chapter 9, Part 1. 

Regarding bis-NHC chelating ligands, several structures that differ in the motifs used for the enlargement of the tether have been proposed as catalysts for the Mizoroki-Heck reaction. They range from non-functionalised aliphatic chains [23-25] to phenyl [26], biphenyl [27], binaphthyls [28] and to chains containing additional coordination positions like ethers [29], amines [30], and pyridines in an evolution towards pincer complexes [31-35], In most cases, the activity of aryl bromides in Mizoroki-Heck transformations was demonstrated to be from moderate to high, while the activation of chlorides was non-existent or poor (Scheme 6.7). 

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)...

The degradation products of GOG were (Vm), GC -Dimer, vanillin (II), and dehydrodivanillin (X). The reaction of GOG by laccase III, therefore, brings about the formation of biphenyl structures, the cleavage of C-C bond between a- and -carbons, and the cleavage of -0-4 ether linkages. The mode of these cleavages is similar to that of SOG. 

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 ... 

As is readily noted from the results summarized in Table 8E.13, enantioselectivity is very sensitive to a variety of factors such as the nucleophile and the nature of the allylic system as well as the ligand used. As expected, the enantioselectivity varied greatly with the structure of the nucleophile. Higher enantioselectivities were consistently obtained from the reactions of 2-cyclopentenyl phenyl ether than from the corresponding reactions of 2-cyclohexenyl ether. The biphenyl-derived DiPHEMP (7a) proved to be more effective than closely related BINAP (4) for this reaction. 

As polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) are compounds with similar structures and monitoring methods, they are discussed together in this chapter. The structures of PCDDs, PCDFs, PCBs, and PBDEs are shown in Fig. 4.1. 

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