Methylmercury hydroxide

Methotrexate, sodium (15475-56-6) Methylmercuric chloride (00115-09-3) Methylroercury chloride (00115-09-3) Methylmercury dicyandiamide (00502-39-6) Methylmercury hydroxide (01184-57-2)... 

METHYLMERCURY(I) CATION see MLF550 METHYLiMERCURY CHLORIDE see MDD750 METHYLiMERCURY DICYANDIAMIDE see MLF250 METHYLMERCURY HYDROXIDE see MLGOOO METHYLiMERCURY (3-HYDROXYQUINOD TE see MLHOOO... 

By contrast, there was no valid evidence of a genotoxic effect on somatic cells of cats chronically exposed to methylmercury orally (Miller et al. 1979). However, only minimal toxicity was observed at the high dose (0.046 mg Hg/kg/day) in this study. Doses of 0.86, 1.7, or 3.4 mg Hg/kg as methylmercury hydroxide administered once by intraperitoneal injection to groups of 2 male CBA mice did not cause an... 

The active substance is easily obtained from methylmercury hydroxide reacted with dicyandiamide ... 

Methylhexafluoroisopropyl(fluorosulfuryl) peroxide, 16 126 Methyllithium, 37 56-57 Methylmercury(ll) hydroxide, 32 205 Methyl methylphenylphospinate, 42 77 iV-Methyl-N-nitrosotoluene-p-sulphonamide, 34 297... 

Table 9.8 lists the strengths of various bases toward the proton (H ) and the methyl-mercury cation (CH1Hg+). Bases such as the sulfide ion (S ) and triethylphosplune (El,P) are very strong toward both the methylmercury ion and the proton, but about a million times better toward the former hence they are considered soft The hydroxide ion is a strong base toward both acids, but in this case about a million times better toward the proton hence it is hard. The aqueous fluoride ion. F, is not a particularly good base toward either add but slightly better toward the proton as expected from its hard character. 

Scheme 2. Reactions between methylmercury(II) hydroxide and 8-azaadenine.

Complexation of 8-azaadenine with methylmercury(II) hydroxide at different pH values gave the coordinated complexes 194-197. Their structures have been established by X-ray analysis (86ICA181) (Scheme 40). 

The thermal decomposition has been discussed (Section IV,E,1). Imidazole forms quaternary salts with methylmercury(II)." l-Acetyl-3-alkylimi-dazolium salts can be dequaternized by hydroxide ion ° or primary amines to the 1-alkylimidazole. 

Likewise the very strong, hard base, hydroxide ion, can displace the weaker soft base, sulfite ion, from the soft acid, methylmercury cation ... 

Hg bond. The compounds most likely to be found under environmental conditions are the mercuric salts HgCl2, Hg(OH)2 and HgS the methylmercury compounds me-thylmercuric chloride (CH3HgCl) and me-thylmercuric hydroxide (CH3HgOH) and, in small fractions, other organomercuries such as dimethylmercury or phenylmercury (US EPA 1997, VoL VI). 

The number of species involved here (MeHg, Me2Hg, Hg and Hg(0)) is small relative to those of some other elements (e.g., arsenic), with only the counterion varying. In the aquatic environment, methylmercury may be present coordinated to chloride, hydroxide, alkanethiol, or various other forms of organic material, either dissolved or in the solid phase. Coordination depends on competition between chemical, biochemical, pH or Eh (oxidation levels), and salinity. Reduction to inorganic mercury or further slow methylation to dimethylmercury may occur (this latter may lead to transport to the atmosphere). Similarly, coordinated methylmercury may enter the sediment layer. This latter may be considered as the main zone for microbial methylation of Hg in view of the high amount of biological activity there. Similar coordination may exist as in the aquatic zone, but with more likelihood of sulfide or alkanethiol complexation. 

Smelters and incinerators also release mercury — crematoria included, because dental fillings are vaporized by the intense heat. Chlor-alkali plants, which produce chlorine and sodium hydroxide from salt, also release significant amounts of mercury. Land erosion is a contributing factor, because it permits mercury compounds in the soil to transfer into water. The flooding of previously wooded land is another factor. Vegetation and soil decompose and release mercury furthermore, in such a bacte-ria-rich environment, mercury converts to methylmercury. Discarded thermometers and batteries release mercury as well. 

For organometallic species, the analytical challenge involves quantitative extraction of the species from the solid phase without appreciable transformation to other forms. Various liquid extractants have been used such as methanolic hydrochloric acid (extraction of organotins). Strong alkali digests (KOFI or tetramethylammonium hydroxide) will dissolve most tissue without breakdown or transformation of arsenic species. As an alternative to liquid extraction, methylmercury species may be extracted from solids using steam distillation. Specific reaction conditions will affect the recovery of various species and rigorous validation of extraction procedures is therefore recommended. 

To extract organically boundmercury from the muscle tissue of fish, Westoo homogenized the fish with water and acidified with concentrated hydrochloric acid (1/5 of the volume of the suspension). Organomercuric compounds were then extracted in one step with benzene using the method described by Gage. Methylmercury could be extracted with difficulty where only a small amount of acid is present (e.g. at pH 1). From an aliquot of the benzene solution, organomercury could be extracted with ammonium or sodium hydroxide solution, saturated with sodium sulphate, for elimination of lipids. The yields were low and variable, but could be improved as described below. 

Uchida et al 2 have shown that the mercury compound in the shellfish that caused the Minimata disease (Japan) was methyl (methylthio) mercury. Westoo concluded that it is reasonable to assume that methylmercury, if present in fish, should at least to some extent be present as a methylthio derivative. The Hg-S bond is stronger than Hg-NH or Hg-OH bonds. Accordingly, the former bond would prevent the formation of the latter types of bonds in the presence of ammonium hydroxide solution and increase the solubility in water. Any methylthio group present should therefore be removed before the extraction with alkali. 

In the method developed by Westoo" described earlier in this section, for the identification and determination of methylmercury in fish by gas chromatography, the methylmercury was extracted with benzene from a homogenate of the fish acidified with hydrochloric acid. It was then taken up into ammonium hydroxide solution and finally re-extracted into benzene after acidification with hydrochloric acid. The extraction with alkali was incomplete unless the benzene extract was previously concentrated by distillation. The distillation procedure was assumed to remove volatile thio compounds binding part of the methylmercury and preventing its uptake into ammonia. Any methylmercury attached to a sulphur atom of nonvolatile compounds giving rise to alkali-insoluble methylmercury salts at the purification stage would not be determined. In fish from Swedish lakes and the Baltic, with total mercury contents... 

When, however, small amounts of methylmercury dicyanidiamide (less than 0.05mg/kg) were added to meat, liver or egg yolk and analysed according to the above method, the methylmercury was completely lost in liver and egg yolk, and only partly recovered from meat. After addition of lOmg/kg of methylmercury to meat or liver, most of it was recovered from meat, but only 5% from liver. Such a failure of the procedure can be expected, if the methylmercury in the neutralized extracts from these foodstuffs is firmly attached, exclusively or to a considerable extent, to thiol groups of nonvolatile compounds, but only if the methylmercury salts formed are insoluble in alkali solutions. Model experiments showed, in fact, that after the addition of excess methanethiol or thiophenol to methylmercury chloride in benzene, an extraction with 2N aqueous ammonia or with sodium hydroxide did not extract the mercury compound from the benzene layer. 

Mercuric Chloride Solution. Dissolve 50g of mercuric chloride and 170ml of concentrated hydrochloric acid in water, and make up to 1000ml with water. Extract any methylmercury or other impurities present by shaking four times with 500ml of benzene for 3 minutes. Purify 10ml of the fourth benzene extract by extraction with ammonium hydroxide solution, acidification with hydrochloric acid and re-extraction into benzene as described below. Gas chromatograph the benzene solution. If a methylmercury peak is found, repeat benzene extractions of the mercuric chloride solution until the test for methylmercury is satisfactory. 

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