2- Chlorophenol, hydrolysis

Polyhalogenobenzene Hydrolysis. The chlorobenzenes can be transformed into chlorophenols by hydrolysis in a Hquid-phase basic medium. The two most commonly used techniques are treatment in aqueous alkaU medium at a temperature between 200 and 350°C (48), or a milder hydrolysis (200—250°C) treatment with dilute sodium hydroxide in the presence of copper. The hydrolysis may be carried out in the vapor phase (250—400°C) on soHd catalysts based on rare-earth phosphates (49) or copper-beating siUca. 

The results for the hydrolysis of chlorobenzene, o-chlorotoluene and p-chloroanisole in presence of cuprous oxide at different temperatures (Fig. 14) show a good selectivity for the reaction of the chlorobenzene. But, the p-chloroanisole is also transformed by a secondary demethylation reaction into the corresponding p-chlorophenolate. 

A large quantity (700 kg) of the chlorophenol, left in contact with cone, sodium hydroxide solution for 3 days, decomposed, attaining red heat and evolving fumes which ignited explosively. Although this could not be reproduced under laboratory conditions, it is believed that exothermic hydrolysis to the hydroquinone (possibly with subsequent aerobic oxidation to the quinone) occurred, the high viscosity of... 

Although anthraquinone is the starting point for the preparation of many derivatives, involving substitution and replacement reactions, certain compounds are obtained directly by varying the components in the above synthesis. Thus, for example, replacement of benzene with methylbenzene (toluene) leads to the formation of 2-methylanthraquinone. A particularly important variation on the phthalic anhydride route is the synthesis of 1,4-dihydroxyanthraquinone (6.6 quinizarin) using 4-chlorophenol with sulphuric acid and boric acid as catalyst (Scheme 6.3). The absence of aluminium chloride permits hydrolysis of the chloro substituent to take place. 

A hydrolysis step is involved in the pulp industry in order to concentrate the cellulose from wood. This uses large-scale processes whereby a liquid fraction, the lignocellulose, is formed as a by-product in the process, and contains high levels of phenolic components and their derivatives. These compounds also constitute an environmental problem due to their possible introduction into rivers, lakes, and/or seas. Chlorophenols from the cellulose bleaching process have traditionally attracted most of the interest in the analysis of industrial waste because of their high toxicity. 

All accidents concerned with PCDD/F are related to the production of chlorophenols. The most famous accident happened in Seveso close to Milan, Italy, on July 10, 1976. ICMESA Corp. manufactured 2,4,5-trichlorophenol for production of phenoxy-herbizides by alkaline hydrolysis of 1,2,4,5-tetrachlorobenzene (see Figure 8.1). This... 

Hydrolysis products that may form in soil and in microbial cultures include A-phenyl-3-chloro-carbamic acid, 3-chloroaniline, 2-amino-4-chlorophenol, monoisopropyl carbonate, 2-propanol, carbon dioxide, and condensation products (Rajagopal et al., 1984). The reported half-lives in soil at 15 and 29 °C were 65 and 30 d, respectively (Hartley and Kidd, 1987). 

The rates and mechanisms of hydrolysis and transesterification of phenyl benzoate in aqueous ethanolic KOH solution were determined by non-linear least-squares regression.4 Kinetic studies of the transesterification of a series of 4-nitrophenyl 3- and 4-substituted benzoates by 4-chlorophenol in DMF in the presence of potassium carbonate at various temperatures were reported.5... 

Enzymes are biocatalysts constructed of a folded chain of amino acids. They may be used under mild conditions for specific and selective reactions. While many enzymes have been found to be catalytically active in both aqueous and organic solutions, it was not until quite recently that enzymes were used to catalyze reactions in carbon dioxide when Randolph et al. (1985) performed the enzyme-catalyzed hydrolysis of disodium p-nitrophenol using alkaline phosphatase and Hammond et al. (1985) used polyphenol oxidase to catalyze the oxidation of p-cresol and p-chlorophenol. Since that time, more than 80 papers have been published concerning reactions in this medium. Enzymes can be 10-15 times more active in carbon dioxide than in organic solvents (Mori and Okahata, 1998). Reactions include hydrolysis, esterification, transesterification, and oxidation. Reactor configurations for these reactions were batch, semibatch, and continuous. 

Hydrolysis of chlorobenzene and the influence of silica gel catalysts on this reaction have been studied by Freidlin and co-workers (109). Pure silica gel gave up to 45% phenol from chlorobenzene at 600°C. When the silica gel was promoted with 2% cupric chloride, up to 75% phenol was obtained (381). A number of other salts were tested by Freidlin and co-workers as promoters, but they exerted an adverse effect on the activity or selectivity of the catalyst. With 0.2% cupric chloride and 6% metallic copper, the activity of silica-gel was doubled (389). At 500° under the above conditions, the halides were hydrolyzed at rates decreasing in the following order chloride, bromide, iodide, fluoride (110). The specific activation of aryl halides by cupric chloride was demonstrated by conversion of chlorobenzene to benzene and of naphthyl chloride to naphthalene when this catalyst was supported on oxides of titanium or tin (111). The silica promoted with cupric chloride was also found to be suitable for hydrolysis of chlorophenols and dichlorobenzenes however, side reactions were too prominent in these cases (112). 

The photolysis of aqueous 3-chloroaniline was found to proceed via a clean photohydrolysis step to give 3-aminophenol with a quantum yield of

hydrolysis process or a fast reaction of a primarily formed aminophenyl cation with H20 (see Scheme 5). 

Ion-pair extraction and IPC were combined to analyze phosphoric acid mono- and diesters originating from the microbial hydrolysis of flame retardants. Even tertiary treatment did not ensure complete removal of the studied compounds detected in municipal wastewater [107], Chlorophenols extracted from water samples as anionic chlorophenolates were studied by IPC because the anionic forms of these analytes provide better UV ultraviolet absorption than uncharged chlorophenol based on their auxochromic effects. IPC conditions yielded adequate retention of the charged analytes and good sensitivity [108]. 

Properties of PCDEs, including physicochemical ones, are not well known as the literature reviews of PCDEs have shown [4, 11,40,46]. PCDEs resemble PCBs structurally and in their chemical and physical properties, which, like PCDDs, PCDFs, and related compounds, are known to be stable and resistant to breakdown by heat, hydrolysis, bases, and acids. PCBs are also quite stable to oxidation under moderate conditions [3], but there is not much data about PCDEs concerning their stability. There is some evidence that PCDEs are resistant to bases and acids and the occurrence of PCDEs in the environment indicates that PCDEs are persistent and bioaccumulating compounds. The study of Firestone et al. [37] already showed that PCDEs are quite stable, since PCDEs could be measured in chlorophenol extracts after sulfuric acid treatment. Tetra- and octachlorinated PCDE congeners were later proven resistant in treatment with... 

According to a patent of the Sumitomo Co. (1965), tris-phenol phosphate is prepared from phenol by esterification with phosphorus oxychloride, which is then chlorinated, yielding after hydrolysis a chlorophenol mixture with an ortho para ratio of 8 1. Using sulfuryl chloride (SO2CI2) as chlorinating agent, a chlorophenol mixture of ortho para ratio 4.1 5.7 is formed in the presence of Lewis acid catalysts. 

Carbon-Ti02 prepared by hydrolysis of TiC with tetrabutylammonium hydroxide followed by calcination Photodegradation of liquid-phase 4-chlorophenol and remazol red of gas-phase CH3CHO, CO, and CeHe The superior photocatalytic activities of carbon-doped materials was demonstrated by photodegradation tests under visible light and diffuse indoor daylight. 156... 

PROBABLE FATE photolysis, based on data for 4-chlorophenol, intramolecular photolysis may be a very important fate, reaction with photochemically produced hydroxyl radicals has a half-life of 1.1 days, will degrade through photolysis if released to water oxidation can occur, but probably cannot compete with biodegradation hydrolysis not important volatilization not important sorption data inconclusive, but potential for adsorption by organics exists biological processes no data on bioaccumulation, biodegradation data not applicable to environment other reactions/interactions can be chlorinated further by chlorine present in HiO... 

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