4-Chloro-1,2-dihydroxybenzene

The facts in favour of the first are that cpiinonc, like a ])cioxicle, has a strong oxidising action, that on reduction it yields, not a glycol, but a dihydroxybenzene moreover, with I CI- instead of a tetra-chloro-deiivative, a dichloroben/cnc is foi ined. In favour of the ketone structure is the formation of a mono- ami di-o ime f(loldschiniclt). 

Chloro-l,U-dihydroxybenzene, AG28 6-Chloro-3,5-dihydroxy- S-tri-azine, AB22... 

All these advanced methods have been compared with anodic oxidation for a 178-ppm 4-chlorophenol solution [140]. The mineralization rate was much faster for the new processes and the substrate was completely transformed into C02 by the Photoelectro-Fenton method, as can be deduced from data given in Fig. 22. In all cases, the initial intermediate was 4-chloro-l,2-dihydroxybenzene, which was further oxidized to yield maleic and fumaric acids with loss of Cl-. The subsequent degradation of these acids gave oxalic acid, which complexes with Fe(III). Such complexes are attacked slowly by OH, but decomposed quickly by UVA light. 

Oxidation of 4-chlorophenol can be brought about by single photodecomposition by hydroxy radicals generated from Fenton s reagent (H2O2 plus Fe ions) . Irradiation in the 320-400 nm range with Fenton s reagent is also effective in the oxidation of 4-chlorophenol . Continuous irradiation at 365 nm has identified two different reaction pathways with formation of the 4-chlorodihydroxycyclohexadienyl radical and also of the chlorophenoxyl radical. The quantum yields of these processes have been determined to be 0.056 and 0.015, respectively . Reaction of 4-chlorophenol with ozone leads to the formation of 4-chloro-l,3-dihydroxybenzene and 4-chloro-l,2-dihydroxybenzene. The latter product is produced in quantity in the presence of hydroxyl radicals . ... 

Chlorocyclohexadienones, synthesis of 651 4-Chloro-l,2/3-dihydroxybenzenes 1085 4-Chloro-l-hydroxynaphthalene, irradiation of 1073... 

Dihydroxy-9(10i/)-anthracenone 380—see also AnthraUn, Dithranol Dihydroxyanthraquinones, chemical shifts for, isotope effects on 345, 346 Dihydroxybenzenes—see also Benzenediols, 4-Chloro-l, 2/3-dihydroxybenzenes, Dihydroxyalkylbenzenes, Hydroxyphenols methylation of 308 synthesis of 408, 409, 411... 

In our own work (ref.39) the methyl, ethyl and benzyl esters of coccinellic anhydride methyl ether were prepared by the Dlels-Alder reaction of 2-chloro and2-bromomaleicanhydride with 3-alkoxy carbonyl-2,4-bistrimethylsiloxypenta-1,3-diene (R = Me,Et,Bn) rather than by the lengthy procedure used formerly (ref. 214). Nevertheless the Friedel-Crafts reaction of these esters with 1,4-dihydroxybenzene to afford finally 6-deoxykermesic add could not be effected. 

As early as 1902 it was recognized that the combination of formanilide and phosphoryl chloride will formylate 1,3-dihydroxybenzene. Though the scope of the reaction was limited, this seminal result foreshadowed the 1925 discovery by Vilsmeier and colleagues that the reaction of N-methylacetanilide and phosphoryl chloride yielded, among other things, 4-chloro-1,2-dimethylquinolinium chloride. ... 

Figure 4 shows the chemical formulae of other epoxy resins commonly used to prepare conductive adhesive compositions. Representative of approximately difunctional compounds are the diglycidyl ether of bisphenol-F (DGEBF) 18 and the diglycidyl ether of 1,3-dihydroxybenzene 19. Epoxy resins with a functionality higher than two are prepared by the reaction of l-chloro-2,3-epoxypropane 7 with polyfunctional starting materials. 

The decomposition of benzene and naphthalene and its homologues by microorganisms has already been discussed earlier. The metabolizing mechanisms of naphthalenes in fish have been well studied [47, 49]. Decomposition products of chlorobenzene in daphnia, mosquitos, snails and fishes are the polar compounds chlorophenol and chloro-o-dihydroxybenzene amongst other compounds, those of nitrobenzene aniline, acetanilide, aminophenols and nitrophenols and those of hexachlorobenzene pentachlorophenol and unknown compounds [71]. Bromoben-zene is deactivated to the toxic bromophenol [217]. In the case of man and land mammals, studies have concentrated on the metabolism of benzene, toluene, xylenes and styrene, which are also significant in occupational medicine [12, 13, 136, 195, 196, 215-217], A comparison of the metabolism of benzene into phenol in various animal species with the aid of microsomal preparations of the lungs or liver yielded vast differences. However, it is possible for benzene, in part, to inhibit or prevent its own metabolism [218]. 

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