Catechol content

Pyrolysis techniques were applied for the evaluation of catechol content of tannins from different plant materials [1,2], or for the quantitation of tannin content in products such as wine [2]. 

In the case of low temperature tar, the aqueous Hquor that accompanies the cmde tar contains between 1 and 1.5% by weight of soluble tar acids, eg, phenol, cresols, and dihydroxybenzenes. Both for the sake of economics and effluent purification, it is necessary to recover these, usually by the Lurgi Phenosolvan process based on the selective extraction of the tar acids with butyl or isobutyl acetate. The recovered phenols are separated by fractional distillation into monohydroxybenzenes, mainly phenol and cresols, and dihydroxybenzenes, mainly (9-dihydroxybenzene (catechol), methyl (9-dihydtoxybenzene, (methyl catechol), and y -dihydroxybenzene (resorcinol). The monohydric phenol fraction is added to the cmde tar acids extracted from the tar for further refining, whereas the dihydric phenol fraction is incorporated in wood-preservation creosote or sold to adhesive manufacturers. Naphthalene Oils. Naphthalene is the principal component of coke-oven tats and the only component that can be concentrated to a reasonably high content on primary distillation. Naphthalene oils from coke-oven tars distilled in a modem pipe stiU generally contain 60—65% of naphthalene. They are further upgraded by a number of methods. 

Figure 2. Dependence of intrinsic catalytic activity, au, and 3-methyl catechol selectivity, Ss,o on the cation type used All cations were added at 5 at.% content.

The selectivity 3,0 is strongly dependent on the Mg content (Fig. 4). It increases with Mg concentrations up to 7 5%, passing through a maximum of S3.0 = 0.65. 3-methyl catechol becomes the main product at low conversion. It is worthwhile to note that only the relative formation of guaiacol and 3-methyl catechol are affected by the percentage of Mg added to alumina, 0-alkylation is reduced in favour of C-alkylation, but the ring methylation stays preferentially ortho-selective. 

To elucidate some enzymatic characteristics of the isolated laccases I, II, and III, substrate specificities for several simple phenols, electrophoresis patterns, ultraviolet spectra, electron spin resonance spectra, copper content, and immunological similarities were investigated. Tyrosine, tannic acid, g c acid, hydroquinone, catechol, pyrogallol, p-cresol, homocatechol, a-naphthol, -naphthol, p-phenylenediamine, and p-benzoquinone as substrates. No differences in the specificities of these substrates was found. The UV spectra for the laccases under stucfy are shown in Figure 4. Laccase III displays three adsorption bands (280, 405, and 600nm), laccase II shows one band 280nm), and laccase I shows two bands (280 and 405 nm). These data appear to indicate differences in chemical structure. The results of the copper content analysis (10) and two-dimensional electrophoresis also indicate that these fractions are completely different proteins (10), Therefore, we may expect differences in substrate specificities between the three laccase fractions for more lignin-like substrates, yet no difference for some simple phenolic substrates. 

Substitution of the terminal amine with ligating groups, such as catecholate, hydrox-amate or diketonate, lead to the formation of A-cis chiral complexes. In these structures the chiral information content is located in the amino acid bridges, instead of the macrocyclic peptide ring structure used in ferrichrome. It should be emphasized... 

Humic acido from ooilo and ligniteo have been examined by ERR spectrometry. All samples showed a stable free organic radical content of about 1018 spins per gram. When these samples were converted to their sodium salts, a marked increase in radical content occurred. This was interpreted to indicate that a quinhydrone moiety exists in the humic acid macromolecule. Synthetic humic acid, prepared by oxidizing catechol in the presence of amino acids, also showed similar ERR spectra, as did selected quinhydrone model compounds. The radical moiety appeared to be stable to severe oxidation and hydrolytic conditions. Reduction in basic media caused an initial decrease in radical species continued reduction generated new radical species. A proposed model for humic acid based on a hydroxyquinone structure is proposed. 

Artificial catechol-amine humic acid Spin content X 10 2.3 54 23... 

Siderophores. If a suitably high content of iron (e.g., 50 pM or more for E. coli) is maintained in the external medium, bacteria and other microorganisms have little problem with uptake of iron. However, when the external iron concentration is low, special compounds called siderophores are utilized to render the iron more soluble.7 11 For example, at iron concentrations below 2 pM, E. coli and other enterobacteria secrete large amounts of enterobactin (Fig. 16-1). The stable Fe3+-enterobactin complex is taken up by a transport system that involves receptors on the outer bacterial membrane.9 12 13 Siderophores from many bacteria have in common with enterobactin the presence of catechol (orftzo-dihydroxybenzene) groups... 

The effects of five phenolic compounds, catechol, protocatechuic, p-coumaric, p-hydroxybenzoic, ferulic acids and their mixture were studied on pH, organic matter, organic-nitrogen, total phenolic content and certain inorganic ions of forest mineral soils (Ae and B horizons). The A- and B-horizon soils, were amended with 104 M concentration of each phenolic compound and their mixture. In general, soil properties were affected by phenolics amendement. However, soils amended with catechol did not influence any of the soil characteristics. Contents of organic matter, nitrogen and phosphate were lower in soils amended with different phenolic compounds compared to the unamended control soil (Inderjit and Mallik, 1997). 

The hydroxylation of phenol on TS-1 is normally operated in a slurry reactor, at temperatures close to 100°C, with total consumption of the oxidant. The selectivities on phenol and H2O2 are generally in the ranges 90-95% and 80-90%, respectively. The hydroquinone to catechol ratio is well in excess of the statistical value of 1 2, owing to lower steric requirements for / -hydro-xylation and the faster diffusion of the p-substituted product (Table 2). Yields and kinetics are strictly related to the content of lattice Ti. It should be emphasized that any extra-framework Ti species, present as impurities on TS-1, are the major source of unproductive side reactions, such as H2O2 decomposition and unselective radical chain oxidations. 

Spectrofluorimetry differs from absorption spectrophotometry in not yielding an absolute scale of values. For this reason it is essential to employ a reference standard for quantitative measurements. For example, some pharmacopoeial tests, such as the test for uniformity of content for digitoxin tablets, employ a spectrofluorimefric assay and comparison wi an ofticial reference standard. Quantitative Spectrofluorimetry has been proposed for a munber of naturally fluorescent compoimds, including ergometrine, riboflavine, tiie catechol-amines, phenothiazines, the barbiturates (at pH 13), and certain antibiotics such as chlortetracycline and oxytetracycline. 

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