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Catechol polymerization

Methyl Vinyl Ketone. Methyl vinyl ketone [78-94-4] (3-buten-2-one) is a colorless Hquid with a pungent odor. It is stable only below 0°C, and readily polymerizes on standing at room temperature. It can be inhibited for storage and transportation by a mixture of acetic or formic acid and hydroquinone or catechol (266). This ketone is completely soluble in water, and forms a binary azeotrope with water (85 MVK 15 H2O vol %) at 75.8°C. [Pg.496]

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials No reactions Stability During Transport Stable Neutralizing Agents for Acids and Caustics Not pertinent Polymerization Polymerization is accelerated by heat and exposure to oxygen, as well as the presence of contamination such as iron rust. Iron surfaces should be treated with an appropriate reducing agent such as sodium nitrate, before being placed into isoprene service Inhibitor of Polymerization Tertiary butyl catechol (0.06 %). Di-n-butylamine, phenyl-beta-naphthylamine andphenyl-alpha-naphthylamine are also recommended. [Pg.222]

Kondo maintained his interest in this area, and with his collaborators [62] he recently made detailed investigations on the polymerization and preparation of methyl-4-vinylphenyl-sulfonium bis-(methoxycarbonyl) meth-ylide (Scheme 27) as a new kind of stable vinyl monomer containing the sulfonium ylide structure. It was prepared by heating a solution of 4-methylthiostyrene, dimethyl-diazomalonate, and /-butyl catechol in chlorobenzene at 90°C for 10 h in the presence of anhydride cupric sulfate, and Scheme 27 was polymerized by using a, a -azobisi-sobutyronitrile (AIBN) as the initiator and dimethylsulf-oxide as the solvent at 60°C. The structure of the polymer was confirmed by IR and NMR spectra and elemental analysis. In addition, this monomeric ylide was copolymerized with vinyl monomers such as methyl methacrylate (MMA) and styrene. [Pg.379]

An anti-oxygen such as catechol or hydroquinone is used to prevent polymerization. Hydroquinone should be added in the ratio of one part per thousand unless the phenylethylene is to be used immediately.1... [Pg.81]

Butadiene CH2=CHCH= H2 Cu Acetylide, Vinyl Acetylene Ethylene Air (Peroxides) > 300 114 Inhibitor — t-Butyl Catechol — 115ppm Activation 12.0 429 Self-polymerization above RT or press... [Pg.821]

Alkynes are reactive toward hydroboration reagents. The most useful procedures involve addition of a disubstituted borane to the alkyne, which avoids complications that occur with borane and lead to polymeric structures. Catechol borane is a particularly useful reagent for hydroboration of alkynes.212 Protonolysis of the adduct with acetic acid results in reduction of the alkyne to the corresponding cw-alkene. Oxidative workup with hydrogen peroxide gives ketones via enol intermediates. [Pg.352]

The OH can react with catechol, by hydrogen abstraction or addition to the aromatic ring, to produce the resonance-stabilized radical The latter could couple with other catechol molecules or oxygen to eventually form polymerized, highly colored materials, according to the scheme proposed for phenol by Voudrias (90) (Figure 6). [Pg.483]

It is interesting to underline that there is another (plant) enzyme which possesses a coordinatively similar dicopper environment catechol oxidase.11 As already mentioned in Chapter 6, Section 3, such an ubiquitous enzyme catalyses the two-electron oxidation by molecular dioxygen of catechols to the corresponding quinones (the so-generated quinones in turn polymerize to form brown polyphenolic catechol melanins, which protect damaged plants from pathogens or insects). [Pg.451]

Even at ambient temperatures, styrene is likely to react with itself— very slowly, but steadily. For this reason, a small amount of polymerization inhibitor, about 10 ppm (parts per million) of para-tertiarybutyl catechol, a chemical whose name nobody wants to remember except its salesman, is added to styrene kept in storage. Since polymerization is promoted by higher temperatures styrene is usually stored in insulated tanks. [Pg.129]

Phenols (p-cresol, guaiacol, pyrogallol, catechol) and aromatic amines (aniline, p-tolidine, o-phenyldiamine, o-dianisidine) are typical substrates for peroxidases [90 -109]. These compounds are oxidized by hydrogen peroxide or hydroperoxides under peroxidase catalysis to generate radicals, which after diffusion from the active center of the enzyme react with further aromatic substrates to form dimeric, oligomeric or polymeric products. [Pg.88]

Like its monomeric counterpart, the polymeric reagent is inert to simple amines, amides, alcohols and phenols, but easily oxidizes thiols to disulphides, phosphines to phosphine oxides, hydroquinone and catechol to quinones, and thioketones, thioesters and trithiocar-bonates to the corresponding 0x0 derivatives, in dichloromethane, chloroform or acetic... [Pg.166]

Phenolic compounds have also been oxidatively polymerized to humic substances by clay minerals (29) and by the mineral fraction of a latasol (66). After a 10-day equilibration period, montmoril-lonite and illite clay minerals yielded 44 to 47% of the total added phenolic acids as humic substances whereas quartz gave only 9%. Samples of a latasol yielded over 63% of the total amount, from mixtures in varied proportion, of mono-, di- and trihydroxy phenolic compounds as humic substances (66). Extractions of the reaction products yielded humic, fulvic, and humin fractions that resembled soil natural fractions in color, in acid-base solubility, and in infrared absorption spectra. Wang and co-workers (67) further showed that the catalytic polymerization of catechol to humic substances was, enhanced by the presence of A1 oxide and increased with pH in the 5.0 to 7.0 range. Thus the normally very reactive products of Itgnin degradation can be linked into very stable humic acid polymers which will maintain a pool of potentially reactive phytotoxins in the soil. [Pg.367]

With tyrosinase, on the contrary, a two-electron oxidation occurs, as no EPR signal was detected in the catechol oxidation at pH 5.3 Melanins are polymerization products of tyrosine, whereby tyrosinase catalyses the first steps the formation of dopa (3,4-dihydroxyphenylalanine) and of dopaquinone, leading to an indolequi-none polymer The peroxidase mechanism for the conversion of tyrosine into dopa in melanogenesis was not substantiated In natural and synthetic melanins free radicals of a semiquinone type were detected by EPR 4-10 x 10 spins g of a hydrated suspension (the material was modified on drying and the number of free spins increased). The fairly symmetrical EPR signal had a g-value of 2.004 and a line-width of 4-10 G The melanins seem to be natural radical scavengers. [Pg.22]

Butadiene is available commercially as a liquefied gas underpressure. The polymerization grade has a minimum purity of 99%, with acetylene as an impurity in the parts-per-million (ppm) range. Isobutene, 1-butene, butane and cis-l- and Zrc//7.s-2-butcnc have been detected in pure-grade butadiene (Miller, 1978). Typical specifications for butadiene are purity, > 99.5% inhibitor (/c/V-butylcatecliol). 50-150 ppm impurities (ppm max.) 1,2-butadiene, 20 propadiene, 10 total acetylenes, 20 dimers, 500 isoprene, 10 other C5 compounds, 500 sulfur, 5 peroxides (as H2O2), 5 ammonia, 5 water, 300 carbonyls, 10 nonvolatile residues, 0.05 wt% max. and oxygen in the gas phase, 0.10 vol% max. (Sun Wristers, 1992). Butadiene has been stabilized with hydroquinone, catechol and aliphatic mercaptans (lARC, 1986, 1992). [Pg.111]

Approximately 50% is used as starting material for insecticides, 35-40% for perfumes and drugs and 10-15% for polymerization inhibitors and other chemicals. Catechol has also been used as an antiseptic, in photography, dyestuffs, electroplating, specialty inks, antioxidants and light stabilizers, and in organic synthesis (Hamamoto Umemura, 1991 Lewis, 1993). [Pg.434]

The more stable boron chelates can be isolated even from aqueous solution, whereas those of lower stabilities are only accessible from non-aqueous media. Catechol- and inositol-borates (3, 5 and 6) possesses a well-defined monomeric structure,75 whereas those obtained from monosaccharides and alditols are polymeric.121 A crystal structure determination122 has been carried out for sodium scyUo-inositol diborate (6). [Pg.95]

Vinylidene Chloride Monoperoxide. When vinyli-dene chloride is stored without a polymerization inhibitor (such as tertiary butyl catechol or other phenol type inhibitors) at a temp of between -40 and +25° in the presence of air or oxygen, the 02 dissolves to form a peroxide compd of undetermined nature which is an extremely violent expl This peroxide seems to act as a polymerization catalyst because its formation is often accompanied by the pptn of a flocculent vinylidene chloride polymer. Since the peroxide is absorbed on the pptd polymer, any separation... [Pg.271]

The simplest, but least accurate, method of assaying DPO activity is to record the final color yield when the enzyme is incubated with a suitable chromogenic substrate such as catechol, DOPA, or 4-methylcatechol. DOPA is the most frequently used substrate in colorimetric assays because it yields a dark brown/black end-product. In this reaction, catecholase catalyzes the conversion of DOPA to dopaquinone and then to the red dopachrome, which subsequently polymerizes to yield dark brown melanin-type pigments. Unfortunately, this simple procedure has serious limitations, as it measures the end-product of a sequence of reactions rather than the true initial reaction rate. Furthermore, because different substrates yield different final colors, valid kinetic comparisons between substrates are not possible. Nevertheless, this simple assay technique has proved adequate for useful comparative studies of the levels of enzymic browning in different fruit varieties and similar problems (Vamos-Vigyazo, 1981 Machiex et al., 1990). [Pg.395]

As an alternative to polymers bearing pendant catechols, Winston and his colleagues have prepared hydroxamic acid polymers in which hydroxamate side-chains were linked by oligomethacroyl units216"218. From experiments on iron-overloaded mice four polymers were found to be as good as, or better, than DFOA in removing iron. Several of the polymers had quite low toxicity. A polymeric form of (25) of around 106 Daltons was particularly effective. [Pg.118]

Peroxidases (EC 1.11.1.7). Peroxidases are hemoproteins, produced mainly by microorganisms and plants, which catalyze oxidation of the recalcitrant nonphenolic lignin units in the presence of hydrogen peroxide (Duran and Esposito, 2000). This is possible because of the formation of a high redox potential oxo-ferryl intermediate during the reaction of the heme cofactor with H202 (Martinez et al., 2005). Dubey et al. (1998) studied the polymerization of catechol by plant peroxidases and found that the resultant polymers consisted of phenylene and oxyphenylene units (Figure 2.14). [Pg.70]

Polymerization of hydroquinone, catechol and pyrogallol (measurement of optical density)... [Pg.73]

Polymerization of pyrogallol (measurement of optical density) ring cleavage of pyrogallol and catechol (measurement of C02 release) yields of humic polymers IR and 13C CPMAS NMR spectra resembling natural HAs... [Pg.74]

Oxidation and polymerization of catechol, pyrogallol and 2,6-dimethylphenol (FTIR spectra) SEM coupled with energy dispersive X-ray spectrometry investigation of reaction products on surface of clay minerals, 13C NMR, MALDI MS study of reaction products... [Pg.74]


See other pages where Catechol polymerization is mentioned: [Pg.9]    [Pg.9]    [Pg.94]    [Pg.521]    [Pg.164]    [Pg.95]    [Pg.195]    [Pg.300]    [Pg.411]    [Pg.480]    [Pg.480]    [Pg.23]    [Pg.693]    [Pg.73]    [Pg.234]    [Pg.321]    [Pg.385]    [Pg.76]    [Pg.76]    [Pg.119]    [Pg.1438]    [Pg.396]    [Pg.52]    [Pg.64]    [Pg.68]    [Pg.74]    [Pg.77]   
See also in sourсe #XX -- [ Pg.52 ]




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