Phenolic groups, chemical

Phenol s chemical properties are characterized by the influences of the hydroxyl group and the aromatic ring upon each other. Although the stmcture of phenol is similar to cyclohexanol, phenol is a much stronger acid. Its piC in aqueous solution at 25°C is 9.89 x 10 ° (8). This characteristic allows aqueous hydroxides to convert phenol into their salts. The salts, especially those of sodium and potassium, are converted back into phenol by aqueous mineral acids or carboxyhc acids. 

These results demonstrate some interesting chemical principles of the use of acrylic adhesives. They stick to a broad range of substrates, with some notable exceptions. One of these is galvanized steel, a chemically active substrate which can interact with the adhesive and inhibit cure. Another is Noryl , a blend of polystyrene and polyphenylene oxide. It contains phenol groups that are known polymerization inhibitors. Highly non-polar substrates such as polyolefins and silicones are difficult to bond with any technology, but as we shall see, the initiator can play a big role in acrylic adhesion to polyolefins. 

Chemical attachment of a detectable component to an oligonucleotide forms the basis for constructing a sensitive hybridization reagent. Unfortunately, the methods developed to crosslink or label other biological molecules such as proteins do not always apply to nucleic acids. The major reactive sites on proteins involve primary amines, sulfhydryls, carboxylates, or phenolates— groups that are relatively easy to derivatize. RNA and DNA contain none of these functionalities. 

In the Colour Index both conventional sulphur dyes and their leuco counterparts are allocated the same Cl constitution number a different number is given to the related solubilised version. Thus, for example, Cl Sulphur Black 1 and Cl Leuco Sulphur Black 1 have the reference Cl 53185 whereas Cl Solubilised Sulphur Black 1 appears under Cl 53186. Because of the complexity of the final products, sulphur dyes are classified according to the chemical structure of the organic starting material that predominates in the manufacturing process. Typical intermediates include aromatic amines, with or without nitro and phenolic groups, and diphenylamine derivatives. 

Another promising prodrug undergoing clinical evaluation is etoposide phosphate. Here, the phenolic group of this chemically complex antitumor... 

A particularly interesting example of bin-uclear Mn electrochemistry is that reported by Holm et al. for the [Mn2(salmp)2]" (n = 2+, 1+, 0,1—, 2—) complex [88]. H3salmp is a pentadentate SB ligand that bridges both Mn centers by means of a centrally positioned phenolate group (7). [Mn2(salmp)2]" undergoes four chemically reversible one-electron transfers. 

We conclude our short discussion of relationships between chemical structure and light absorbance by considering some cases in which an acid or base function forms part of a chromophore. Important examples of compounds exhibiting such chro-mophores are phenols and anilines. As is evident from the spectra shown in Fig. 15.5, deprotonation of a phenolic group results in a substantial bathochromic shift... 

These acid-catalyzed reactions occur at temperatures lower than those used in conventional liquefaction processes. Phenol induces acid-catalyzed solvolytic reactions at temperatures as low as 120°C. The liquefied products contain chemically bound phenolic groups, a portion of which can be recovered by cracking. 

Creating acidic groups (carboxylic acids and phenol groups) on the internal soot surface by chemical oxidation with, e.g., chromic acid, fixation of cationic complexes of the catalyst (e.g., amino complexes of Pt(II) or Pt(IV) at the inner surface of the soot particles by ion exchange, followed by chemical or electrochemical reduction of these complexes... 

A reasonable model has been proposed to accommodate these results (2/y 23). The presence of quinoid functions in lignin would give rise to electron donor-acceptor complexes with existing phenolic groups. These complexes, like quinhydrone, would form stable radical anions (semiquinone anions) on basification, according to the scheme shown below. Both biological and chemical oxidation would create more quinone moieties, which in turn would increase the contribution of Reactions 1 and 2. Alternately, enzymatic (< ) and/or alkaline demethylation 16) would produce... 

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