2-Ethylphenol activation

Sudol uses fractions of coal tar rich in xylenols and ethylphenols. It is much more active and less corrosive than lysol, and remains more active in the presence of organic matter. The phenol coefficients of sudol against Mycobacterium tuberculosis, Staphylococcus aureus, and Pseudomonas aeruginosa are 6.3, 6, and 4, respectively. It also is slowly sporicidal (97). 

Aryl alcohol oxidase from the ligninolytic fungus Pleurotus eryngii had a strong preference for benzylic and allylic alcohols, showing activity on phenyl-substituted benzyl, cinnamyl, naphthyl and 2,4-hexadien-l-ol [103,104]. Another aryl alcohol oxidase, vanillyl alcohol oxidase (VAO) from the ascomycete Penicillium simplicissimum catalyzed the oxidation of vanillyl alcohol and the demethylation of 4-(methoxymethyl)phenol to vanillin and 4-hydro-xybenzaldehyde. In addition, VAO also catalyzed deamination of vanillyl amine to vanillin, and hydroxylation and dehydrogenation of 4-alkylphenols. For the oxidation of 4-alkylphenol, the ratio between the alcohol and alkene product depended on the length and bulkiness of the alkyl side-chain [105,106]. 4-Ethylphenol and 4-propylphenol, were mainly converted to (R)-l-(4 -hydroxyphenyl) alcohols, whereas medium-chain 4-alkylphenols such as 4-butylphenol were converted to l-(4 -hydroxyphenyl)alkenes. 

The enzyme p-ethylphenol methylene hydroxylase (EPMH), which is very similar to PCMH, can also be obtained from a special Pseudomonas putida strain. This enzyme catalyzes the oxidation of p-alkylphenols with alkyl chains from C2 to C8 to the optically active p-hydroxybenzylic alcohols. We used this enzyme in the same way as PCMH for continuous electroenzymatie oxidation of p-ethylphenol in the electrochemical enzyme membrane reactor with PEG-ferrocene 3 (MW 20 000) as high molecular weight water soluble mediator. During a five day experiment using a 16 mM concentration of p-ethylphenol, we obtained a turnover of the starting material of more than 90% to yield the (f )-l-(4 -hydroxyphenyl)ethanol with 93% optical purity and 99% enantiomeric excess (glc at a j -CD-phase) (Figure 14). The (S)-enantiomer was obtained by electroenzymatie oxidation using PCMH as production enzyme. 

After the decarboxylation step, vinylphenols may be reduced to ethylphenols but the sequential decarboxylase and reductase activities, regarding wine yeasts, have only been demonstrated in D. bruxellensis and in P. guilliermondii (Barata et al. 2006). The former species may also convert 4-VP into 4-EP in the absence of hydroxycinnamic acids (Dias et al. 2003b). 

Dekkera brwcellensis Spoilage yeast Active hydroxycinnamate decarboxylase and vinylphenol reductase producing ethylphenols in synthetic media, juices and wines Heresztyn (1986) Chatonnet et al. (1995) Shinohara et al. (2000) Rodrigues et al. (2001) Dias et al. (2003a, 2003b)... 

Pichia guilliermondi Contamination yeast Active hydroxycinnamate decarboxylase and vinylphenol reductase producing ethylphenols in synthetic media and grape juices Barata et al. (2006)... 

Recently, AEDA and SHA-0 yielded 41 and 45 odor active compounds for Scheurebe and Gewurztraminer wines, respectively (P). Ethyl 2-methylbutyrate, ethyl isobutyrate, 2-phenylethanol, 3-methylbutanol, 3-hydroxy-4,5-dimethyl-2(5H)-furanone, 3-ethylphenol and one unknown compound, named wine lactone, showed high flavor dilution (FD)- factors (Table I) in Gewurztraminer and Scheurebe wines. 4-Mercapto-4-methylpentan-2-one belongs to the most potent odorants only in the variety Scheurebe whereas cis-rose oxide was perceived only in Gewurztraminer (Table I). 4-Mercapto-4-methylpentan-2-one was identified for the first time in Sauvignon blanc wines (JO). The unknown compound with coconut, woody and sweet odor quality, which has not yet been detected in wine or a food, was identified as 3a,4,5,7a-tetrahydro-3,6-dimethylbenzofuran-2(3H)-one (wine lactone) (JJ). 

Model complexes of peroxidase were used as catalysts for the oxidative polymerization of phenols. Hematin, a hydroxyferriprotoporphyrin, catalyzed the polymerization of />ethylphenol in an aqueous DMF.63 Iron—A/,A/ -ethylenebis(salicylideneamine) (Fe—salen) showed high catalytic activity for oxidative polymerization of various phenols.64 The first synthesis of crystalline fluorinated PPO was achieved by the Fe—salen-catalyzed polymerization of 2,6-difluorophenol. Cardanol was polymerized by Fe— salen to give a cross-linkable polyphenol in high yields. 

Particles of the enzymatically synthesized phenolic polymers were also formed by reverse micellar polymerization. A thiol-containing polymer was synthesized by peroxidase-catalyzed copolymerization of p-hydroxythiophenol and p-ethylphenol in reverse micelles [70], CdS nanoparticles were attached to the copolymer to give polymer-CdS nanocomposites. The reverse micellar system was also effective for the enzymatic synthesis of poly(2-naphthol) consisting of qui-nonoid structure [71], which showed a fluorescence characteristic of the naphthol chromophore. Amphiphilic higher alkyl ester derivatives were enzymatically polymerized in a micellar solution to give surface-active polymers at the air-water interface [72, 73]. 

Rather unique, though related, is the activation of 2-ethylphenol by 211, which affords predominantly the carbene 580 in admixture with the f/ -alkene complex 581 (ca. 10%, Scheme 61). This is presumed to occur by initial alcoholysis of one Ir-Ph linkage, affording intermediate N that then undergoes double activation of the methylene C-H bonds. Significantly, as with ethers (vide supra), the first C-H activation is preferentially followed by a-, not jS-activation, thus favouring the... 

Finally, the iridium carbene complex 580, obtained from the double C-H activation of 2-ethylphenol by Tp Ir(C6H5)2(N2) (211), illustrates the rare incidence of an equilibrium between alkylidene hydride and alkene hydride complexes. The alkylidene forms in admixture with ca. 5% of the alkene hydride isomer 581, illustrating a preference for the a- over hydrogen in the second activation step. However, in isolation 581 is observed to re-establish the same equilibrium mixture (i.e. 20 1 580 581, Scheme 61) a rare example of a metal-alkene converting to a metal-alkylidene, the reverse reaction being more typical. 

The adsorption of phenols from aqueous electrolyte solution has been studied from a different point of view by Peschel, Belouschek, Kress, and Reinhard. Instead of measuring the adsorption as a function of pH or of solute concentration they measured the adsorption of fixed concentrations (2x10 "m) of phenol, p-cresol, and 4-ethylphenol by active carbon at four temperatures between 20 and 38 "C as a function of supporting electrolyte (NaCl) concentration. The objective of this work was to seek evidence for multimolecular hydrate layers at the carbon surface. Earlier work on the... 

In addition, the solubility of phenolics in water is generally regarded as an important factor for their adsorption. It is believed that the lower the solubility of phenolics, the easier the attachment to the activated carbon surface, and as a result, a higher adsorptive capacity can be achieved. However, the adsorptive capacity of phenolics did not follow the order of their water solubility except 2-nitrophenol. They found this phenomenon can be explained by the significant different molecular structures of phenolics. 2-Methylphenol and 2-ethylphenol are three dimensional while 2-chlorophenol and phenol are two dimensional. The adsorbate dimensions played a more important role in the adsorption of phenolics on ACFs due to the narrow PSD of ACFs. As shown in Figure 6.2, the differences of adsorptive capacity on ACC-10 were small as compared to F400. 

FIGURE 6.4 Adsorption isotherms of 2-ethylphenol. (a) F400, (b) ACC-10, and (c) ACC-15. (Reprinted from Chemosphere, 55, Lu, Q. and Serial, G.A., Adsorption of phenolics on activated carbon—Impact of pore size and molecular oxygen, 671-679, Copyright 2002, with permission from Elsevier.)... 

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