Hydrogen peroxide-Trichloroacetic acid

Trichloroacetic acid is manufactured in the United States by the exhaustive chlorination of acetic acid (38). The patent Hterature suggests two alternative methods of synthesis hydrogen peroxide oxidation of chloral (39) and hydrolytic oxidation of tetrachloroethene (40). 

All three chloroacetic acids (chloroacetic acid [MCA], dichloroacetic acid [DCA], and trichloroacetic acid [TCA]) are naturally occurring (7), with TCA being identified in the environment most frequently (reviews (278, 405 108)). However, these chlorinated acetic acids also have anthropogenic sources. The major source of natural TCA appears to be the enzymatic (chloroperoxidase) or abiotic degradation of humic and fulvic acids, which ultimately leads to chloroform and TCA. Early studies (409) and subsequent work confirm both a biogenic and an abiotic pathway. Model experiments with soil humic and fulvic acids, chloroperoxidase, chloride, and hydrogen peroxide show the formation of TCA, chloroform, and other chlorinated compounds (317, 410-412). Other studies reveal an abiotic source of TCA (412, 413). 

Hirvonen et al. (1995) evaluated the feasibility of the UV/H202 process for the removal of trichloroethylene (TCE) and erythromycin (perchloroethylene [PCE]) in contaminated groundwater. The formation of chloroacetic acids (CAs) was used as an indication of partial degradation. The dominant byproduct, dichloroacetic acid (DCA), accounted for the major part of the total yield of CAs. The observed concentrations of trichloroacetic acid (TCA) and DCA were relatively low compared with the total amount of TCE and PCE degraded. The effect of initial concentrations of the parent compounds, hydrogen peroxide, and bicarbonate on the yield of by-product was inves-... 

The usual acid-sensitivity of acyclic acetals was similarly of no avail in the related system studied by Myers and co-workers [Scheme 2.53].111 In this case, treatment of the dimethyl acetal 55.1 with trichloroacetic acid generated an oxonium ion intermediate, that was rapidly and efficiently intercepted with hydrogen peroxide - a reagent which is much more nucleophilic than water. The resultant a-methoxyhydroperoxide 53 was then reductively cleaved under neutral conditions to produce a hemiacetal, which lost methanol to give the desired aldehyde 53.3. 

Quite recently, List and coworkers observed that when hydrogen peroxide is used as an oxidant, the same reaction furnishes stable and isolable cyclic peroxyhemike-tals [26]. When using the primary amine catalyst 20-trichloroacetic acid (10 mol%), the oxidation of both linear and branched acyclic enones with aqueous hydrogen peroxide (3 equiv) at 30 °C in dioxane gave the peroxyhemiketals 26 in reasonable yields with high enantioselectivities (94—95% ee) (Scheme 5.20). Cyclic peroxyhemiketals were further transformed via a simple protocol (treatment with 1 N NaOH)... 

It has been hypothesized on the basis of the formation of trichlo-roacetate from aliphatic compounds, especially acetate, by the action of chloroperoxidase in the presence of hydrogen peroxide and chloride that this might be a naturally occurring metabolite (Haiber et al. 1996). Plausible mechanisms for the formation of trichloroacetic acid by atmospheric reactions involving trichloro-ethane and tetrachloroethene are discussed in Section 4.1.2. 

Corrosion can be a problem, especially if a chlorine-containing compound is decomposed. This may require that the reactor be made of titanium. The corrosion can be reduced by the use of sodium carbonate.207 Use of this system at 380°C reduced the content of polychlorinated biphenyls in a sample from 20 mg/L to less than 0.5 /tg/L. Trichloroethylene, 1,1,1-trichloroethane, and trichloroacetic acid were destroyed with 99.96% efficiency at 450°C for 60 ss using 1.5% hydrogen peroxide plus sodium bicarbonate.208 Sodium nitrate or sodium nitrite could be used in place of the hydrogen peroxide. Nitrates, ammonium hydroxide, and amines, all are converted to nitrogen at 350-360 C. Emulsions of petroleum, water, and solids can be broken by heating to 350oC. Supercritical water has been used to recover 2,4-diamino-toluene from distillation residues from the manufacture of 2,4-toluenediisocyanate.209... 

Mb-CMC fihn was made by casting solution of myoglobin and carboxymethyl cellulose (CMC) on pyrolytic graphite electrode. Trichloroacetic acid (TCA), nitrite, oxygen, and hydrogen peroxide can be catalytically reduced at the Mb-CMC film electrode. When TCA was added to a pH 3.0 buffer, an increase in the MbFe reduction peak at about -0.2 V was observed, accompanied by a decrease of the MbFe oxidation peak. The reduction peak current increased as the TCA concentration increased. The catalytic reduction peak current showed a linear relationship with TCA concentration in the range of 7.5 X 10 - 2 X 10 M. Compared with the direct reduction... 

These acids, their esters and also o-phenylphenol, can be detected by introducing 0.02% of an optical bleach such as Ultraphor WT (Firm 16) into the adsorbent layer [22]. The substances may further be visualised by spraying with a rhodamine B solution (Rgt. No. 220) or a bromo-cresol green solution (Rgt. No. 25). Special spray reagents have been described for specific detection of the different types of preservative e. g., thiobarbituric acid (Rgt. No. 248) or thymol-sulphuric acid for sorbic acid hydrogen peroxide-ferric chloride for dehydroacetic acid and ferric chloride for salicylic acid. o-Phenylphenol, a fungicide, can be visualised with 2,6-dichloroquinonechloroimide (Rgt. No. 66), diazotised 4-nitroani-line solution (Rgt. No. 182) or cerium-(IV) sulphate-trichloroacetic acid (Rgt. No. 37). 

A patent [60] states that batch polymerizations of 7V-vinylpyrrolidone in aqueous solution with hydrogen peroxide often give rise to gel formation. This difficulty can be overcome by replacing at least part of the water with such substances as isopropyl alcohol, thioglycolic acid, dimethylformamide, ethanolamine, methyl ethyl ketone, trichloroacetic acid or 2-mercaptoethanol. A continuous polymerization procedure is said to be particularly effective. Procedure 3-9 is given here only as an illustration of this patented process. 

Higher carboxylic acids such as acetic acid and propionic acid have also been used to epoxidize PBD [100]. Acetic acid is known not to react below 40°C with hydrogen peroxide to form a peracid therefore, a strong protraiic acid is added to catalyze peroxide formation [116]. Mineral acids such as sulfuric acid [117,118] or phosphoric acid [118] are effective for this. Trichloroacetic acid was found to induce epoxide opening faster than the epoxidation [118]. 

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