Oxidation methyl mercury

SuIfona.tlon, Sulfonation is a common reaction with dialkyl sulfates, either by slow decomposition on heating with the release of SO or by attack at the sulfur end of the O—S bond (63). Reaction products are usually the dimethyl ether, methanol, sulfonic acid, and methyl sulfonates, corresponding to both routes. Reactive aromatics are commonly those with higher reactivity to electrophilic substitution at temperatures > 100° C. Tn phenylamine, diphenylmethylamine, anisole, and diphenyl ether exhibit ring sulfonation at 150—160°C, 140°C, 155—160°C, and 180—190°C, respectively, but diphenyl ketone and benzyl methyl ether do not react up to 190°C. Diphenyl amine methylates and then sulfonates. Catalysis of sulfonation of anthraquinone by dimethyl sulfate occurs with thaHium(III) oxide or mercury(II) oxide at 170°C. Alkyl interchange also gives sulfation. 

With respect to Cr a distinction should be made between Cr(III), which is the common oxidation state in the soils, being rather immobile and so toxic, and Cr(VI), which is very mobile and very toxic. With respect to Hg, the situation is even more complex, due to the occurrence of mercuric mercury (Hg2+), mercurous mercury (Hg2+), elemental mercury (Hg°) and organic mercury species, such as methyl mercury, (CH3)2Hg (see Section 18.5). Furthermore, volatilization of elemental mercury and organic mercury species is common. A description of these... 

Mercury is unusual in that it is found in the environment as both oxidized mercury ions and as reduced methyl mercury. The mercurous (Hg+) ion is... 

Mercury occurs in soils predominantly in the +2 oxidation state. Elemental Hg in the atmosphere is oxidized to Hg + and deposited in rainfall. It is a strong chalcophile and under anaerobic conditions forms the extremely insoluble sulfide cinnabar (HgS, pK = 52.7). Nonetheless it is not entirely immobilized under anaerobic conditions because it is reduced to volatile Hg° or methylated to volatile methyl mercury compounds by microbial action, and so returned to the atmosphere. The methylation is mediated by various bacteria, especially methanogens, through the reactions ... 

Mercury(II) perchlorate. 6 (or 4)dimethyl sulfoxide, 4073 Mercury(II) Af-perchlorylbenzylamide, 3644 Mercury(II) peroxybenzoate, 3630 Mercury(II) picrate, 3427 Mercury(II) sulfide, 4602 Mercury(II) thiocyanate, 0975 Mercury(I) nitrate, 4604 Mercury(I) oxide , 4608 Mercury(I) thionitrosylate, 4605 Mercury, 4595 Mercury nitride, 4610 Mercury peroxide, 4601 (9-MesitylenesuIfonylhydroxylami ne, 3164 Methacryloyl chloride, see 2-Methyl-2-propenoyl chloride, 1453 f Methanamine, see Methylamine, 0491... 

Literally hundreds of complex equilibria like this can be combined to model what happens to metals in aqueous systems. Numerous speciation models exist for this application that include all of the necessary equilibrium constants. Several of these models include surface complexation reactions that take place at the particle-water interface. Unlike the partitioning of hydrophobic organic contaminants into organic carbon, metals actually form ionic and covalent bonds with surface ligands such as sulfhydryl groups on metal sulfides and oxide groups on the hydrous oxides of manganese and iron. Metals also can be biotransformed to more toxic species (e.g., conversion of elemental mercury to methyl-mercury by anaerobic bacteria), less toxic species (oxidation of tributyl tin to elemental tin), or temporarily immobilized (e.g., via microbial reduction of sulfate to sulfide, which then precipitates as an insoluble metal sulfide mineral). 

The impact of some metals is strongly related to their chemical form rather than to their total concentration. For instance, arsenic is generally toxic in both its As(III) arsenite and As(V) arsenate forms, but is nontoxic in its organic forms, such as arsenocholine. Mercury, on the other hand, is toxic in all forms but is substantially more toxic as methyl mercury than it is in the elemental state. Chromium in the Cr(III) oxidation state is less toxic and less soluble than it is in the Cr(VI) state. 

Bis(phenylselanyl)methyllithiums 429 (R = H) are stable till 0 °C and were initially trapped with deuterium oxide, methyl iodide and benzophenone639. a-Substituted organolithium intermediate 429 (R = Me, w-CgH ), prepared with LiTMP in THF/HMPA at — 20 °C, reacted with alkyl bromides, ethylene oxide and benzaldehyde to give products 430 in good yields (Scheme 113)640. Bis(methylselanyl)methyllithiums 431 have been allowed to react with different electrophiles to afford products 432 (Scheme 113)640. Alkylated products have been deprotected with mercury(II) chloride or copper(II) chloride/copper(II) oxide, and by oxidation with hydrogen peroxide or benzeneseleninic anhydride644. Deprotection of selenoacetals to ketones can also be performed with sulfuric acid645. 

Minamata is an industrial city on the Yatsushiro coast of Japan on the southernmost island (K5rushu). In the city there was a factory that manufactured the chemicals vinyl chloride (used to make the plastic PVC see pp. 168-71) and acetaldehyde for many years. The processes used inorganic mercury (mercuric oxide) as a catalyst. The effluent from the factory contained inorganic mercury and perhaps also some organic mercury (methyl mercury), produced as a by-product in the chemical reaction in the plant. This effluent was discharged into the waters of Minamata Bay. 

Mercury (Hg, CAS Number 7439-97-6) is a naturally-occurring metal that has an atomic number of 80 and an atomic weight of 200.6. Many different organic and inorganic mercury compounds are found in nature because of mercury s ability to form covalent and ionic bonds with other chemicals. Mercury exists in three forms in three oxidation states (0, +1, +2) elemental mercury (Hg°), organic mercury (e.g., methyl mercury), and inorganic mercury (e.g.. 

For mercury determination in sediments or fish tissues, samples were oxidized with boiling nitric acid. After reagent addition the methyl mercury derivate was extracted by benzene. The results of gas-chromatographic determination were higher than those obtained by wet-oxidation and atomic absorption methods . ... 

The metabolic product of the metal can determine the action in the organ in which the metal is deposited. Usually, metabolism of metals can lead to detoxification and often to excretion. Some metals, such as selenium metal and oxides, are converted to the volatile trimethyl derivative and are exhaled. On the other hand, mercury is converted to methyl mercury chloride, which is soluble in lipids and appears to be concentrated overtime in organs with high lipid content. 

Sarafian T, Verity MA. 1991. Oxidative mechanisms underlying methyl mercury neurotoxicity. IntJ Dev Neurol 9(2) 147-153. 

CARBENES, GENERATION Benzyltrieth-ylammonium chloride. Dehydro-N,N, N -tricyclohexylguanidinohexacarbonyldi-iron(O). Ethylene oxide. Ethyl trichloro-acetate. Phenyl(l-bromo-l-chloro-2,2,2-trifluoroethyI)mercury. Phenyl(trihalo-methyl)mercury. Trimethyl-silyldiazo-methane. 

Metals Lead, calcium, arsenic, methyl mercury, organotins (TBTO, i.e., bis(tris- -butyltin)oxide), nickel Appears to depend of speciation of metal [35]... 

This element is a chalcophile, and in unweathered rocks is most commonly found as the mineral cinnabar (HgS). In soil environments, the cationic form, is most common, as the reduced oxidation state (+1) has a limited stability range. Reduction to the metallic elemental form, H, is easily achieved in soils by both biological and chemical reactions. Elemental mercury is somewhat volatile, and the vapor is extremely toxic to organisms. Under anaerobic conditions at least, soil microbes methylate mercury, forming volatile organomercury compounds that are bioavail-able and present a health hazard. At the same time, however, anaerobic conditions can convert Hg into the exceedingly insoluble sulhde, HgS. Some of the more important transformations possible for mercury in soil are summarized in Figure 9.9. 

Carbene generation Alumina—Potassium hydroxide. Bis(tribromomethyl)mercury. Bis (trimethylsilyldichloromethyl)mercury. Bromotrifluoromethane. n-Butyllithium. Copper (II) acetylacetonate. Diazoacetaldehyde. Di-n-chloro-x-allyldipalladium. Dichloromethyl 2-chloroethyl ether. Dicyanodiazomethane. sym-Difluorotetrachloroacetone. Ethylene oxide. Methyl dichlorofluoroacetate. Methyllithium. Phenyl (trichloromethyl)mercury. Sodium chlorodifluoroacetate. Sodium trichloroacetate. Thallous ethoxide. / -Toluene-sulfonyl-hydrazine. 

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