Polyhalogenated phenol

The first organic chemical tags, based on polyhalogenated phenols, were introduced by Ohlmeyer et al. [19] and subsequently modified by Nestler et al. [20] an example for both strategies will be presented. 

Mechanistic studies of phototransformation of polyhalogenated phenols have been carried out by means of product analysis. A particular concern is the possibility of the formation of highly toxic polychlorinated dibenzodiox-ins (PCDDs) and dibenzofurans (PCDFs). In a detailed study of the photolysis of 2,4,5-trichlorophenol, already reviewed earlier [8], it was argued that ho-... 

Reactive, unstable compounds, as well as covalent binders, can be removed from screening collections by substructure searches [21, 22]. At Roche, a global team of experienced medicinal chemists has defined more than 100 functionalities which are reviewed at regular intervals. This list has been augmented by unwanted features (e.g., polyacids, alkyl aldehydes, polyhalogenated phenols, etc.) which are chemically unattractive starting points for a hit-to-lead optimization, because they often result in non-optimizable SAR patterns. These chemotypes have been coded into Markush-type substructures for automated detection and removal of unwanted compounds. However, we need to stress that these filters are fully customizable, and removed chemotypes can be restored if required. 

The polyhalogenated phenols are species with three or more halogen atoms. The first such species is pentafluorophenol. The enthalpies of formation predicted from the related pentafluorobenzene are (s) —1056.1, (Iq)—1045.2 and (g) —985.5 kJ mol . These values are some 30-40 kJ moH more negative than the measured values, the largest destabilization observed so far. Before questioning the reliability of the data, consider the thermochemical differences for the gas phase reaction 14 where X = CH3, OH, F, Cl, Br and I ... 

Since polyhalogenated dibenzofuans (PHDFs) contaminate PCBs and polyhalogenated phenols, their cutaneous effects are discussed under those headings. 

This short list, still remarkable for its simplicity, led inevitably to the organometallic compounds and polyhalogenated phenol derivatives — active ingredients which are both highly effective and highly persistent and which may indeed be termed biocides , since they are harmful not only to micro-organisms, but also to plants, insects, snails, fish and other organisms — in short, to all forms of life. 

Determination of Polyhalogenated Phenolic Compounds in Drinking Water, Human Blood Serum and Adipose Tissue... 

For ecological and toxicological reasons, polyhalogenated phenols such as tri-, tetra- or pentachlorophenol are no longer in use. 

A number of the reactions of phenols are typical of ends. Thus they are readily halogenated in the ortho and para positions, with a marked tendency for polyhalogenation. Bromination of phenol with bromine in carbon tetrachloride gives 4-bromophenol, but 2,4,6-tribromophenol is formed with bromine water. 

In the case of polyhalogenated systems, a partial substitution to afford halogenated phenols can be achieved. For instance, treatment of 1,2,4-trichlorobenzene with sodium hydroxide at 130 °C gives 2,5-dichlorophenol in 93% yield. ... 

Analytes CB, chlorobenzenes DDE, l,l-dichloro-2,3-bis(4-chlorophenyl)ethane DDT, l,l-dichloro-2,3-bis(4-chlorophenyl)ethylene DBF, decabromobiphenyls HBCD, Hexabromo-cyclododecane HpBB, heptabromobiphenyl PBB, polybrominated biphenyl PBCCH, pentabromochlorocyclohexane PBDE, polybrominated diphenyl ether PBT, Polybutylene terephthalate PCB, Polychlorinated biphenyl PBDD, polybrominated dibenzo-/ -dioxins PBDF, polybrominated dibenzofuranes PCN, polychlorinated naphthalenes PCP, polychlorinated phenols PBB, polybrominated biphenyl PeBDE, pentabromodiphenyl ether PET, Polyethylene terephthalate PXDDs, polyhalogenated dibenzo-p-dioxins PXDFs, polyhalogenated dibenzofurans TBBPA, tetrabromobisphenol A TBPA, tetrabromophthalic anhydride TCBPA, tetrachlorobisphenol A TDBPP, tris(2,3-dibromopropyl)phosphate. 

Direct oxidation of polyhalogenated aromatic compounds to phenols or quinones, or para-substituted phenols to quinones, is thought to occur by a variant of ipso-substitution. Pentaf-luorochlorobenzene is thus oxidized to tetraflu-... 

The Grob fragmentation is a useful synthetic tool for the construction of rings with six to eight members beginning with a bicyclic structural moiety. One example enables the production of substituted benzenes from readily available bicycles. Khan demonstrated that polyhalogenated (chloro and bromo) phenols (e.g., 36) result from treatment of bicyclic ketones (e.g., 35) with PTSA in toluene. ... 

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