Cresol isomers, oxidation

All cresol isomers can be rapidly removed from environmental media. The dominant removal mechanism in air appears to be oxidation by hydroxyl radical during the day and nitrate radical at night, with half-lives on the order of a day. In water under aerobic conditions, biodegradation will be the dominant removal mechanism half-lives will be on the order of a day to a week. Under anaerobic conditions, biodegradation should still be important, but half-lives should be on the order of weeks to months. In soil under aerobic conditions, biodegradation is also important, but half-lives are less certain, although probably on the order of a week or less. 

Figure 10.11 offers the general reaction network for the SCWO of cresol. This network shows three parallel paths for the oxidation of cresol by SCW. Three reaction intermediates are a hydroxybenzaldehyde via oxidation of the methyl substitute ring-opening products and phenol via demethylation. The end products are COz and HzO. The relative importance of the parallel pathways depends on the specific cresol isomer being oxidized. Figure 10.11 shows that phenol and hydroxybenzaldehydes are key organic intermediates in the reaction network, so the reaction network should also include the reaction paths for these compounds. Two parallel primary paths produce... 

Gas-Liquid Chromatography. Oxidation products were analyzed using either a Pye Argon, Perkin-Elmer Fll or Pye F104 gas chromatograph. The stationary phases and operating conditions have been reported previously 21). An improved method for separating cresol isomers (28) was introduced in this research in place of the previous method which used tris(2,4-xylenyl) phosphate as the liquid phase. 

It has been shown e that two mechanisms, elimination-addition (benzyne) and SN2 displacement, are operative in the liquid-phase hydrolysis of halogenatcd aromatic compounds. The formation of isomeric phenols as a result of the availability of the benzyne route makes the reaction of limited synthetic value. The incorporation of the copper-cuprous oxide system suppresses reaction via the benzyne route, so that the present method has general utility for the preparation of isomer-free phenols. For example, >-cresol is the only cresol formed from -bromotoluene under the conditions of this preparation. 

Other reported syntheses include the Reimer-Tiemann reaction, in which carbon tetrachloride is condensed with phenol in the presence of potassium hydroxide. A mixture of the ortho- and para-isomers is obtained the para-isomer predominates. -Hydroxybenzoic acid can be synthesized from phenol, carbon monoxide, and an alkali carbonate (52). It can also be obtained by heating alkali salts of -cresol at high temperatures (260—270°C) over metallic oxides, eg, lead dioxide, manganese dioxide, iron oxide, or copper oxide, or with mixed alkali and a copper catalyst (53). Heating potassium salicylate at 240°C for 1—1.5 h results in a 70—80% yield of -hydroxybenzoic acid (54). When the dipotassium salt of salicylic acid is heated in an atmosphere of carbon dioxide, an almost complete conversion to -hydroxybenzoic acid results. They>-aminobenzoic acid can be converted to the diazo acid with nitrous acid followed by hydrolysis. Finally, the sulfo- and halogenobenzoic acids can be fused with alkali. 

Isomerization of arene oxides to phenols proceeds by complex and often multiple pathways660 668 that show a marked dependence on pH. Arene oxides as key intermediates provide the basis for explaining the ortho/meta/para isomer ratios observed in enzymatic hydroxylations.655a,b For example, the absence of m-cresol in the metabolites of toluene can be attributed to the fact that none of the three possible isomers of toluene oxide rearranges to this product. 

Of the three isomeric cresols ortho-, meta-, and para-, only m- cresol can be used as the starting material for introducing three nitro groups, viz. in the 2,4,6-positions. Ortho and p- cresols are able to form stable nitro group systems only when no more than two nitro groups are introduced. Under the conditions of the nitration of m- cresol to its trinitro derivative the o- and p- isomers are oxidized to oxalic acid. 

From 100 parts of commercial meta-cresol containing only 60% of the m- isomer (the rest being p- cresol) not more than 100 parts of trinitro-m-cresol can be obtained, p- Cresol is fully oxidized to oxalic acid, which then crystallizes from the spent acid. 

Direct oxidation of p-cresol to p-hydroxy benzaldehyde is a difficult reaction. However, experimental investigations conducted in various industrial R D centers and research and educational institutions revealed that unlike the other two isomers, p-cresol can be directly oxidized to p-hydroxy benzaldehyde by selecting a proper catalyst... 

Manufacturing process In spite of all efforts, no effective catalyst system was yet found commercially viable to either directly oxidize m-cresol or the intermediate ether m-cresyl methyl ether (mcme) unlike other two isomers, p-cresol, o-cresol, or PCMC/OCME. 

Ammoxidation of p-methoxytoluene (protection of the OH group in the p-cresol feed by methylation) over vanadium-titanium oxide catalysts gives p-methoxy-benzonitrile in 65 % yield [81,82]. Because of the greater reactivity of p-methoxy-toluene compared with the m isomer the ammoxidation of m,p-methoxytoluene mixtures results in the formation of only p-methoxybenzonitrile and the m isomer remains mainly unreacted. This presents the possibility of reactive separation of differently substituted toluenes [82]. 

CRESOLS (mixed isomers) (1319-77-3) CyHgO Combustible solid or liquid. Forms explosive mixture with air (flash point >178°F/>81°C autoignition temp 1038-1110 F/559-599°C Fire Rating 2). Incompatible with strong acids, oxidizers, acetaldehyde, alkalis, aliphatic amines, amides, chlorosulfonic acid, nitric acid fuming sulfuric acid (oleum). Liquid attacks most plastics and rubber, although butyl... 

AMINO-3-PYRIDINE (462-08-8) Combustible solid (flash point about 328°F/164°C, based on p-isomer). Forms a strong base with water. Incompatible with strong oxidizers, acids, organic anhydrides, acrylates, alcohols, aldehydes, alkylene oxides, substituted allyls, cellulose nitrate, cresols, caprolactam solution, epichlorohydrin, ethylene dichloride, isocyanates, ketones, glycols, nitrates, phenols, vinyl acetate. Exothermic decomposition with maleic anhydride. Increases the explosive sensitivity of nitromethane. 

XYLIDINE, MIXED ISOMERS (1300-73-8) Combustible liquid (flash point 205°F/96°C). Violent reaction with strong oxidizers, strong acids, nitrosyl perchlorate. Mixtures with hypochlorites form sensitive explosive chloroamines. Incompatible with aldehydes, nonoxidizing mineral acids, cellulose nitrate (of high surface area), cresols, isocyanates, nitrates, nitric acid, organic anhydrides, phenols, sulfuric acid. 

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