Phenols description

Many of the properties of phenols reflect the polarization implied by the resonance description The hydroxyl oxygen is less basic and the hydroxyl proton more acidic in phenols than m alcohols Electrophiles attack the aromatic ring of phenols much faster than they attack benzene indicating that the ring especially at the positions ortho and para to the hydroxyl group is relatively electron rich... 

The kinetics of hydrogenation of phenol has already been studied in the liquid phase on Raney nickel (18). Cyclohexanone was proved to be the reaction intermediate, and the kinetics of single reactions were determined, however, by a somewhat simplified method. The description of the kinetics of the hydrogenation of phenol in gaseous phase on a supported palladium catalyst (62) was obtained by simultaneously solving a set of rate equations for the complicated reaction schemes containing six to seven constants. The same catalyst was used for a kinetic study also in the liquid phase (62a). 

A number of handbooks and monographs are available with detailed descriptions of a variety of plant products and their use (Shahidi and Naczk, 1995). From a more practical point of view, an interlaboratory comparison between six university and industry laboratories of 17 extracts of spices, teas, coffees, and grape skin and of tomato peel slurry established within the framework of an EU sponsored programme, would be of interest (Schwarz et al, 2001). In this collaboration, detailed chemical analysis of the content of different phenolic compounds is compared with six antioxidant assays for the 17 extracts including different extraction procedures. 

Phenolic antioxidants in rubber extracts were determined indirectly photometrically after reaction with Fe(III) salts which form a red Fe(II)-dipyridyl compound. The method was applicable to Vulkanox BKF and Vulkanox KB [52]. Similarly, aromatic amines (Vulkanox PBN, 4020, DDA, 4010 NA) were determined photometrically after coupling with Echtrotsalz GG (4-nitrobenzdiazonium fluoroborate). For qualitative analysis of vulcanisation accelerators in extracts of rubbers and elastomers colour reactions with dithio-carbamates (for Vulkacit P, ZP, L, LDA, LDB, WL), thiuram derivatives (for Vulkacit I), zinc 2-mercaptobenzthiazol (for Vulkacit ZM, DM, F, AZ, CZ, MOZ, DZ) and hexamethylene tetramine (for Vulkacit H30), were mentioned as well as PC and TLC analyses (according to DIN 53622) followed by IR identification [52]. 8-Hydroquinoline extraction of interference ions and alizarin-La3+ complexation were utilised for the spectrophotometric determination of fluorine in silica used as an antistatic agent in PE [74], Also Polygard (trisnonylphenylphosphite) in styrene-butadienes has been determined by colorimetric methods [75,76], Most procedures are fairly dated for more detailed descriptions see references [25,42,44],... 

Model of Dissolution. Based on the results described above, a model for the dissolution of phenolic resins in aqueous alkali solutions 1s proposed. The model 1s adapted from Ueberrelter s description for polymer dissolution 1n organic solvents (.21). In Ueberrelter s model, the dissolution process takes place 1n several steps with the formation of (a) a liquid layer containing the dissolved polymer, (b) a gel layer, (c) a solid swollen layer, (d) an infiltration layer, and (e) the unattacked polymer. The critical step which controls the dissolution process is the gel layer. In adapting h1s model to our case, we need to take into account the dependence of solvation on phenolate ion formation. There 1s a partition of the cation and the hydroxide ion between the aqueous solution and the solid phase. The... 

Talsky [1] illustrated the practical use of higher-order derivative spectrophotometry in estimating pollutants in soils by detailed descriptions of the simultaneous estimation of aniline in waste water, phenol in soils and the study of nickel adsorbed on to bentonite powder. 

Humic and fulvic acids contain various types of phenolic and carboxylic functional (hydrophilic) groups as well as aromatic and aliphatic moieties which import hydro-phobic properties to these substances. Fig. 4.12 gives a schematic idea on the composition of these substances. We refer to the book of Thurman (1985) and Aiken et al. (1985) for a description of the various properties of humic and fulvic acids in soils and waters and the book by Buffle (1988) for the coordinating properties of humus and humic acids. 

As we have seen (pp. 50 et seq.) the reaction between phosphorus oxydichlorofluoride and alcohols, phenols and thiols, affords dialkyl, dicyctoalkyl, diaryl phosphorofluoridates and dialkyl phosphorodithiolates. In a Report1 to the Ministry of Supply on fluorophosphonates a description was given of a new type of nitrogen fluorophosphonate formed by the action of 4 mol. of aniline on 1 mol. of phosphorus oxydichlorofluoride, the fluorine atom being unaffected ... 

An elegant methylating agent for phenols is furnished by diazomethane. A description of its use for this purpose is given later. 

The primary purpose of this chapter is to provide public health officials, physicians, toxicologists, and other interested individuals and groups with an overall perspective of the toxicology of phenol. It contains descriptions and evaluations of toxicological studies and epidemiological investigations and provides conclusions, where possible, on the relevance of toxicity and toxicokinetic data to public health. 

The effect of phenol on benzo[a]pyrene (B[a]P) carcinogenicity has been examined (Van Duuren and Goldschmidt 1976 Van Duuren et al. 1971, 1973). Dermal application of 3 mg phenol in acetone simultaneously with 5 g B[a]P resulted in significantly fewer tumors than application of B[a]P alone. Application surface areas were not reported and could not be estimated from the description of the application procedure. Mice treated dermally with B[a]P followed by dermal application of brewed tea on alternate days over a period of 55 days developed epithelial cell carcinoma or exhibited various stages of squamous cell tumors (Kaiser 1967). The brewed tea contained an unspecified level of phenol, the presumed cancer promoter in this experiment, as well as cresols and dimethylphenols. 

Description of the model. Benzene and its metabolites (phenol, catechol, and hydroquinone) were assumed to compete for the same reaction site on the enzyme cytochrome P-450 2E1. In addition, phenol can undergo both oxidation and conjugation, although the enzymes for each of these reactions are localized in different compartments of the liver, and competition between them is thereby regulated. 

The versatility of permanganate as an oxidant has been greatly enhanced in the past decade by the observation that it can be solubilized in nonaqueous solvents with the aid of phase transfer agents (1). The literature contains descriptions for the use of this procedure for the oxidation of alkenes (2-13), alkynes (13-18), aldehydes (19), alcohols (20), phenols (21,22), ethers (23), sulfides (24,25), and amines (20,26). The dehydrogenation of triazolines has also been achieved by the use of permanganate and a phase transfer agent (27). ... 

The chemistry of phenolic resins is complex. Even today it is not fully understood. The brief description that follows is definitely an oversimplification of the reactions involved. 

The familiar positive photoresists. Hunt s HPR, Shipley s Microposit, Azoplate s AZ etc., are all two-component, resist systems, consisting of a phenolic resin matrix material and a diazonaphthoquinone sensitizer. The matrix material is essentially inert to photochemistry and was chosen for its film-forming, adhesion, chemical and thermal resistance characteristics. The chemistry of the resist action only occurs in the sensitizer molecule, the diazonaphthoquinone. A detailed description of these materials, their chemical structures and radiation chemistry will be discussed in Section 3.5.b. 

The above description of the process is tentative because it is based on limited data. If it is correct, the predominate structures in the PHBA-modified products have amorphous PA/AA/NPG center sections end-capped with single units or short blocks of oligomeric PHBA. Random distribution of the PHBA cannot be ruled out, but the hetero-geneiety of the products suggests that a substantial fraction of PHBA is incorporated into short blocks. The FT-IR and GPC data are consistent with the proposal that short, phenolic-tipped oligomers are the predominant structure present. The possibility that the materials are physical mixtures of oligo-PHBA and amorphous diols can be virtually ruled out on the basis of the extreme insolubility of oligo-PHBA (IJ) and of the model PHBA-benzoic acid adduct synthesized in this study. These materials separate readily from solutions and dispersions of PHBA copolymers. 

Quinone oximes and nitrosoarenols are related as tautomers, i.e. by the transfer of a proton from an oxygen at one end of the molecule to that at the other (equation 37). While both members of a given pair of so-related isomers can be discussed separately (see, e.g., our earlier reviews on nitroso compounds and phenols ) there are no calorimetric measurements on the two forms separately and so discussions have admittedly been inclusive—or very often sometimes, evasive—as to the proper description of these compounds. Indeed, while quantitative discussions of tautomer stabilities have been conducted for condensed phase and gaseous acetylacetone and ethyl acetoacetate, there are no definitive studies for any pair of quinone oximes and nitrosoarenols. In any case. Table 4 summarizes the enthalpy of formation data for these pairs of species. 

A number of ACE assays dealing with the characterization of interactions between cyclodextrines as auxiliary substances and drugs have been presented. Other authors put more emphasis on the description of separation phenomenona by determination of binding constants. Model substances such as phenols are often used to examine the influence of ligand size and substitution as well as to evaluate the mathematical approaches for the calculation of binding constants. 

Table 16.2 lists more than 80 examples of new isoprenylated chalcones reported in the period 1992 to 2003 (see also Figure 16.7). Almost half of the compounds described here are from the Leguminosae, a trend that is also evident in earlier surveys. Other plant families that are well represented in Table 16.2 are the Moraceae and the Cannabinaceae. The literature on isoprenylated flavonoids in general has been reviewed by Barron and Ibrahim to the end of 1994 57 jjjg phenolic constituents of Glycyrrhiza species (licorice), among which are many isoprenylated chalcones, were the subject of an extensive review that includes literature published up to the end of 1996. Nomura and Hano have reviewed the literature on isoprenylated phenolic compounds of the Moraceae to the end of 1993. More recent descriptions of isoprenylated flavonoids are available for the hop plant, Humulus lupulus (Cannabinaceae),and the Moraceae genera Artocarpus and Dorstenia. ... 

Berchemia zeyheri (Rhamnaceae), a tree native to southern Africa which is prized for its beautiful wood, known as pink ivory or red ivory. The complexity of the phenolic compounds present in heartwood extracts prompted their analysis as permethylated derivatives. Stereochemical features were determined by using both NMR and circular dichroism spectroscopy of the parent compounds and their degradation products. These methods were used successfully to obtain a full stereochemical description of the zeyherin epimers 374 and 375, ° which were first isolated in 1971 but not fully characterized at that time. Subsequent work has led to the discovery of further auronol dimers and novel heterodimers with flavanone or isoflavanone constituents as summarized in Table 16.15. ° ° °... 

This limited overview on the analysis of four classes of the following secondary potato metabolites is, except for anthocyanins, largely limited to our own studies of glycoalkaloids, calystegine alkaloids, and phenolic compounds. Because interest in these potato constituents arises from potential health benefits and occasional toxicity, we also include in this overview a brief discussion of these aspects that relate to composition and a description of experimental methods. The interested reader should consult the cited references for an entry into the extensive worldwide literature on the diverse analytical and biological aspects for these metabolites. 

To test the potential of PLS to predict odour quality, it was used in a QSAR study of volatile phenols. A group of trained sensory panelists used descriptive analysis (28) to provide odour profiles for 17 phenols. The vocabulary consisted of 44 descriptive terms, and a scale fiom 0 (absent) to S (very strong) was used. The panel average sensory scores for the term sweet were extracted and used as the Y-block of data, to be predicted from physico-chemical data. 

Acide carboMque (Fr). Phenol Acid Egg or Blowcase is a type of "displacement pump"(qv) used for transferring acids and other corrosive liquids from one apparatus to another by means of compressed air. Its description is given in Refs 1 2. 

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