Mercury compounds, synthesi

Methyl ketones are important intermediates for the synthesis of methyl alkyl carbinols, annulation reagents, and cyclic compounds. A common synthetic method for the preparation of methyl ketones is the alkylation of acetone derivatives, but the method suffers limitations such as low yields and lack of regioselectivity. Preparation of methyl ketones from olefins and acetylenes using mercury compounds is a better method. For example, hydration of terminal acetylenes using HgSO gives methyl ketones cleanly. Oxymercuration of 1-olefins and subsequent oxidation with chromic oxide is... 

In many syntheses activation is not effected by sonochemical preparation of the metal alone but rather by sonication of a mixture of the metal and an organic reagent(s). The first example was published many years ago by Renaud, who reported the beneficial role of sonication in the preparation of organo-lithium, magnesium, and mercury compounds [86]. For many years, these important findings were not followed up but nowadays this approach is very common in sonochemistry. In another early example an ultrasonic probe (25 kHz) was used to accelerate the preparation of radical anions [87]. Unusually for this synthesis of benzoquinoline sodium species (5) the metal was used in the form of a cube attached to the horn and preparation times in diethyl ether were reduced from 48 h (reflux using sodium wire) to 45 min using ultrasound. 

Mercury(II) nitrate is used in the preparation of other mercury compounds in organic synthesis and as an analytical standard for mercury. 

The use of mercury has the merit of easy preparation of the aryl mercury compounds directly from the aromatic compound and an inorganic mercury salt, sometimes in complete regioselective manner. Preparation of the other metallated species generally involves more synthetic steps. An example of a radiofluorode-mercuration reaction (Scheme 29) is the synthesis of 6-p F]fluorometaraminol... 

Nervous System. The nervous system is also a common target of toxic metals particularly, organic metal compounds (see Chapter 16). For example, methylmercury, because it is lipid soluble, readily crosses the blood-brain barrier and enters the nervous system. By contrast, inorganic mercury compounds, which are more water soluble, are less likely to enter the nervous system and are primarily nephrotoxicants. Likewise organic lead compounds are mainly neurotoxicants, whereas the first site of inorganic lead is enzyme inhibition (e.g., enzymes involved in heme synthesis). 

Kochetkov continued as lecture assistant until 1951, combining this work with research on metalloorganic chemistry in Nesmeyanov s laboratory. He studied organo-mercury compounds, in particular their synthesis by the addition of mercuric chloride to acetylenes. In 1948 Nikolay wrote a thesis and received the Ph.D. degree in chemistry. 

One of the very important traditional uses for alkyl mercury compounds has been their use as reagents in preparations of more reactive organometallic compounds. The trifluoromethyl mercurial is also beginning to demonstrate a similar utility as a precursor, for example, in the synthesis of the more reactive reagent (CF3)2Cd glyme. The latter material is clearly a superior agent for the formation of products of only limited thermal stability, since it is active at ambient temperatures and the reactions generally require only a few minutes, or at most a few hours. 

The most notorious mercury compounds in the environment are monomethyl mercury (CH3Hg+) salts and dimethylmercury ((CH3)2Hg). The latter compound is both soluble and volatile, and the salts of the monomethylmercury cation are soluble. These compounds are produced from inorganic mercury in sediments by anaerobic bacteria through the action of methylcobalamin, a vitamin B12 analog and intermediate in the synthesis of methane ... 

The synthesis of trimethyl-2 59) or triethylsilyl lithiums38,6S3) may be effected via the corresponding mercury compound ... 

The easy decomposition of the mercury compounds can be used in direct synthesis of disilanes ... 

The photophysics and photochemistry of gaseous PuFe have been ex-amined. Studies involving zinc porphyrins have been reported and include photo-oxidations in aqueous solution, photoreductions of Zn-TPP with hydrazines, and the role of Zn-TPPSa/ethyl viologen in photoredox processes. The mechanism of the photo-oxidation of water to oxygen with silver chloride has been discussed, and the synthesis of bis(chlorosilyl)-mercury compounds described. Colloidal CdSe has been shown to sensitize the photoreduction of O2 and of methyl viologen by cysteine. ... 

Tor a review of the use of phenyl(trihalomethyl)mercury compounds as dihalocarbene or dihalocarbenoid precursors, see Seyferth, D. Acc. Chem. Res. 1972, 5, 65. For a review of the synthesis of cyclopropanes with the use of organomercury reagents, see Larock, R.C. Organomercurcury Compounds in Organic Synthesis, Springer, NY, 1985, pp. 341-380. 

In a study of six mercury compounds, mercury chloride, mercury nitrate, sodium ethylmercurithi-osalicylate, methyl mercury chloride, mercury acetate and phenylmercury acetate in MDCK cells, LLC-PKl cells and human primary proximal tubular cells (hPTC) and non-renal cell lines (SAOS and Hep G2) it was found that all mercury compounds were toxic to all cell types as evidenced by neutral red uptake, thymidine incorporation and the MTT assay [189]. However, sodium ethylmercurithiosalicylate, methyl mercury chloride and phenylmercury acetate were one order of magnitude more toxic than the other compounds. In addition the GSH synthesis inhibitor L-buthionine sulfoximine (BSO) potentiated the toxicity of all mercury compounds [189]. In a study using primary rabbit proximal tubular cells it was also shown that methyl mercury chloride is more toxic than mercury chloride [190]. Differences in the extent and rate of metal uptake were also evident. Maximum cellular uptake of Hg " occurred within 6-24 hr after exposure and was not concentration-dependent, whereas maximum uptake of CHgHg" occurred within 3 hr of exposure and was concentration- dependent [190]. 

Monomethylmercury (MMM) is the most toxico-logically prominent of organic mercury compounds due to its environmental ubiquity and high potential for bioconcentration. Although DMM is less frequently encountered, it exhibits a far more toxic profile. Based on the lethality of only a few drops of the substance, DMM has been classified as a supertoxic chemical. Absorption of 100 pi of the colorless liquid is equivalent to a severely toxic dose of 100-200 mg of mercury per 100 ml of whole blood. Its synthesis, transportation, and use should be minimized and exercised with only extreme care. 

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