4-Chlorophenol, reaction with

Another appHcation of 4-chlorophenol is in the synthesis of a dmg, ethyl a, a-dimethyl-4-chlorophenoxy acetate [637-07-0] (60), used as a cholesterol-reducing agent. This synthesis involves reaction with acetone and chloroform, followed by ethanol esterification. 

Both pathways have been shown to be relevant for PCDD/F formation in municipal-waste incinerations. Chlorophenols can be converted to PCDD by copper species known in synthetic chemistry as the Ullmann type II coupling reaction. By use of isotope labeling techniques in competitive concurrent reactions with both reactions performed in laboratory experiments it was shown that precursor theory pathways from chlorophenols may be more important compared to the de novo pathway, but either competing pathway strongly depends on such conditions as temperature, air flow rate, and residence time. It may be difficult to model the complex reahty of large incinerators using relevant laboratory experiments. 

The reaction of methyl 10, l l -dihydropyrrolo[ l, Z-b [ l, 2,5]bcnzothiadiazcpinc-l l -acetate 5,5-dioxide 73 or the corresponding ethyl ester 74 with potassium hydroxide in EtOH at 25 °C gave the acid 75 (Scheme 14), which upon treatment with trifluoroacetic anhydride in tetrahydrofuran (THF) underwent intramolecular cyclization to afford 76. The 1,2,5-thiadiazepines 73 and 74 were then heated with an excess of concentrated ammonium hydroxide to give the carboxamide 77. The acid 75 upon reaction with 4-chlorophenol, 4-chlorobenzyl alcohol, or 4-chloroaniline in the presence of iV-(3-dimethylaminopropyl)-iV -ethylcarbodiimide hydrochloride (EDCI) and 4-dimethylaminopyridine (DMAP) afforded the respective esters and amide 78-80 <1996FES425>. 

Ferrihydrite catalysis of hydroxyl radical formation from peroxide has also shown experimental results consistent with a surface reaction [57]. The yield of hydroxyl radical formation was lower for ferrihydrite than for dissolved iron, resulting in a higher peroxide demand to degrade a given amount of pollutant. As mentioned above, although ferrihydrite exhibited a faster rate of peroxide decomposition than goethite or hematite, the rate of 2-chlorophenol degradation with these catalysts was fastest for hematite [55], In other studies, quinoline oxidation by peroxide was not observed when ferrihydrite was used as catalyst [53]. 

Another approach is the introduction of some transition metals, such as Cr, V, Fe, Cu, Mn, Co, Ni, Mo, and La into the synthesis mixture of the MCM-41, MMS with a Si/Me ratio of 80 [85], It was then demonstrated that the presence of the transition metal salts in the gel during the hydrothermal synthesis process hinders the action of the template, which results in MCM-41 pores that are not well formed. These materials were then loaded with TiOz, via the solgel method, and the activity of the Ti02/TM-MCM-41 catalysts in the degradation of the 4-chlorophenol reaction was tested in the presence of UV and/or visible light. It was shown that although some metals are deleterious, others can improve the performance of photocatalysts and even enable them to utilize visible light [85],... 

The starting point for the metallation sequence was /7-chlorophenol, whose directing power was first maximised by conversion to the carbamate 3. Ortholithiation and reaction with N,N-diethylcarbamoyl chloride gave the amide 4. The second ortho carbonyl substituent was then introduced simply by allowing the lithiated carbamate 5 to undergo an anionic ortho-Fries rearrangement to the bis-amide 6. The phenol was protected as its methyl ether 7. 

Phosphorylation. Chambers et al. found the reagent useful for the preparation of nucleoside diphosphoric acids (3, R —adenine, uracil, etc.). A nucleotide (I) is converted into the 5 -phosphoramidate (2) by reaction with ammonia and dicyclo-hexylcarbodiimide (DCC), and the amidate (2) is treated with dioxane diphosphate in o-chlorophenol (3 hrs..0 ). The diphosphoric acid (3) is precipitated with petroleum ether and purified as the ammonium salt. Yields are around 90%, whereas when 8.5% phosphoric add was used yields were in the order of 50-60%. However, anhydrous... 

The equilibrium constant for reaction of 4-chlorophenolate ion with acetyl 4-dimethylaminopyridinium ion is given by ... 

Chlorine dioxide is determined from its absorbance as the coloured product (Xmax = 490 nm) of its reaction with tyrosine [48]. Chlorine dioxide has been found to reduce the absorbance of Acid Chrome Violet K [49]. Spectrophotometric methods of determining CIO2 with the use of Chlorophenol Red have been proposed [50,51]. A scheme for analysing mixtures of Cf, CIO, CIO2, ClO.i, CIO4 , and CIO2 using spectrophotometric and other methods has been devised [52]. 

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... 

Chlorinated Hydrocarbons Short-chain alkyl halides find extensive use as solvents and are common contaminants of ground water. Polychlorinated biphenyls are global contaminants as a consequence of their extensive use and persistence. Chlorinated dioxins and furans are produced as combustion by products or contaminants in reactions with chlorophenols. Consequently, there has been considerable interest in defining the physical chemical properties that determine their environmental behavior. 

Figure 6.6 Reaction sequences for the photochemical degradation of p-chlorophenol. [Reproduced with permission from P. Boule, C. Guyon, A. Tissot, and J. Lemaire, Specific Phototransformation of Xenobiotic Compounds Chlorobenzenes and Halophenols , in R. G. Zika and W. J. Cooper, Eds, Photochemistry of Environmental Aquatic Systems, ACS Symposium Series No. 327, pp. 10-26. Copyright 1985, American Chemical Society.]...

When the irradiation was carried out in aerated solution, the formation of hydroquinone was enhcuiced, p-benzoquinone and hydroxy p-benzoquinone were also formed. 0 products detected Involve radical intermediates. Radicals can react either with chlorophenol or with other radicals and many products can be formed. The reaction is not specific. The photohydrolysis exists (formation of hydroquinone in degassed acidic solution ) but it is only a minor pathway. 

Where selective introduction of substituents into the anthraquinone molecule is difficult, synthesis from smaller components is frequently used. The most important reaction component in this context is phthalic anhydride, which undergoes Friedel-Crafts reaction with other substituted aromatics such as chlorobenzene, chlorophenol or toluene to yield the desired anthraquinone derivative. 

Formation of phenol very likely requires an ipso addition of C02 to chlorobenzene, as shown in reaction (R35). The ipso position was also reported to be the preferred site for hydroxyl radical addition to chlorobenzene." The bimolecular reaction of the ipso adduct C02 CHD with HO-CHD radicals of chlorobenzene is an alternative reaction channel yielding benzoic acid, HCI and chlorophenol, reaction (R36). Elimination of HC02 from the ipso adduct, reaction (R37), and subsequent reaction with HO-CHD radicals leads to the formation of phenol, HCI and chlorophenol," reaction (R38). 

VNS hydroxylation of nitroarenes with alkylhydroperoxides proceeds according to mechanism similar to that of the reaction with a-halocarbanions— reversible nucleophiUc addition, followed by the base-induced p-ehmination of alcohols from the intermediate a"-adducts. These mechanistic features were established by detramination of effects of base on the rate of the reaction, namely, on the competition between VNS hydroxylation and S Ar of chlorine in 4-chloronitrobenzene and 2,4-dinitrochlorobenzene. For instance, the reaction of these hydropaoxides with 2,4-dinitrochlorobenzene carried out in the presence of an excess of f-BuOK proceeds exclusively as VNS to give 2,4-dinitro-5-chlorophenol, whereas in the presence of equimolar amount of f-BuOK substantial quantity of 2,4-dinitrophenol, product of S,.jAr is formed (Scheme 11.43) [66]. 

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