Alkyl mercurials

Alkyl mercury compounds were used widely in the United States as seed disinfectants until prohibited in 1970. Subsequentiy, in 1972, the EPA prohibited the use of ah mercury compounds in agriculture (15). 

Toxicity. Inorganic mercury compounds, aryl mercury compounds, and alkoxy mercurials are generahy considered to be quite similar in their toxicity. Alkyl mercury compounds are considered to be substantiahy more toxic and hazardous. Mercury and its compounds can be absorbed by ingestion, absorption through the skin, or by inhalation of the vapor. The metal itself, however, rarely produces any harmful effects when ingested (16). 

Alkyl mercury compounds in the blood stream are found mainly in the blood cehs, and only to a smah extent in the plasma. This is probably the result of the greater stabhity of the alkyl mercuric compounds, as well as their pecuflar solubiUty characteristics. Alkyl mercury compounds affect the central nervous system and accumulate in the brain (17,18). Elimination of alkyl mercury compounds from the body is somewhat slower than that of inorganic mercury compounds and the aryl and alkoxy mercurials. Methylmercury is eliminated from humans at a rate indicating a half-life of 50—60 d (19) inorganic mercurials leave the body according to a half-life pattern of 30—60 d (20). Elimination rates are dependent not only on the nature of the compound but also on the dosage, method of intake, and the rate of intake (21,22). 

Alkyl mercury halides participate in a photo-sdmidated rathcM chain reacdon of the anion of nitroalkanes Isee Eq. 5.38 in which a 375-W sun lamp Is used." Primary, secondary, and ternary alkyl rathcMs generated from alkyl mercury halides react with the anion of ttitroalkanes to form new C-C bonds. 

Borg, K., Wanntorp, H., Erne, K., and Hanko E. (1969). Alkyl mercury poisoning in terrestrial Swedish wildlife. Viltrevy 6, 301-379. 

Organic solvents Organo(alkyl)mercury Oiganoarsenicals Ozone... 

Wallin K. 1984. Decrease and recovery patterns of some raptors in relation to the introduction and ban of alkyl-mercury and DDT in Sweden. Ambio 13 263-265. 

Organic compounds such as terminal alkynes can undergo direct mercuration using various mercury salts. For instance, alkyne 61 has been shown to react with Hg(OAc)2 to form the symmetrical bis-alkyl-mercury complex 62 (Equation (21)).73... 

Ealy [ 75 ] also used conversion to alkyl mercury iodides for the gas chromatographic determination of organomercury compounds in benzene extracts of water. The iodides were then determined by gas chromatograph of the benzene extract on a glass column packed with 5% of cyclohexane-succinate on Anakron ABS (70-80 mesh) and operated at 200 °C with nitrogen (56 ml min-1) as carrier gas and electron capture detection. Good separation of chromatographic peaks was obtained for the mercury compounds as either chlorides, bromides, or iodides. The extraction recoveries were monitored by the use of alkylmer-cury compounds labelled with 203 Hg. 

Longbottom et al. [40] have described gas chromatographic methods for the determination of alkyl mercury in soils and sediments. 

This very rich chemistry has been the subject of several comprehensive reviews, including recent ones sp carbon centres, general (Kornblum, 1975, 1982 Russell, 1970, 1987), photochemically induced reactions (Bowman, 1988a), substituted aliphatic nitro-compounds (Bowman, 1988b), alkyl mercurials (Russell, 1989) sp carbon centres, general (Norris, 1983 Rossi and... 

Similarly, several examples of reactions of perliuoroalkyl halides have been demonstrated to follow an SrnI -type mechanism (Section 3, p. 75). Since, here too, dissociative electron transfer is likely under the conditions of the reactions [Section 2, pp. 54-56 (Andrieux et ai, 1990b)], the substitution process most probably also follows mechanism (134) rather than (103). The same is also likely to be true with alkyl mercurials (Russell, 1989). 

Molds and other plant diseases are controlled by fungicides, which act to affect the growth or metabolism of fungal pests. Many different fungicides exist, including sulfur, aryl- and alkyl-mercurial compounds, Aw-dithiocarbamates, and chlorinated phenols. 

Toxicology. Organo (alkyl) mercury compounds cause dysfunction of the central nervous system (CNS) and kidneys and are irritants of the eyes, mucous membranes, and skin methyl mercury causes developmental effects in humans. 

The biological half-life in humans for methyl mercury is about 70 days because elimination is slow, irregular, and individualized, there is a considerable risk of an accumulation of mercury to toxic levels. A precise relationship between atmospheric levels of alkyl mercury and concentrations of mercury in blood or urine has not been shown. Clinical observations indicate that concentrations of 50-100pg mercury/lOOml of whole blood may be associated with symptoms of intoxication concentrations around 10-20pg mercury/ 100 ml are not associated with symptoms. In a study of 20 workers engaged in the manufacture of organic mercurials and exposed for 6 years to mercury concentrations in air between 0.01 and O.lmg/m, there was no evidence of physical impairment or clinical laboratory abnormalities. Low levels of methyl mercury in the blood do not seem to affect the results of behavioral performance tests. ... 

The alkyl mercury halides are irritating to the eyes, mucous membranes, and skin and may cause severe dermatitis and burns skin sensitization has occasionally occurred. ... 

American National Standard Acceptable Concentrations of Organo (Alkyl) Mercury, ANSI Z37.30-1969. New York, American National Standards Institute, 1970... 

Contraindications Acute renal impairment, organic (short-chain alkyl) mercury poisoning, G6PD deficiency (unless a life-threatening situation exists), hepatic insufficiency (unless due to arsenic poisoning), use of iron, cadmium or selenium poisoning, hypersensitivity to dimercaprol or any component of the formulations... 

S S342 Alkyl mercury compounds 0.01 (TWA) Carbosieve Thermal desorption Flame-. 004-.017 (TWA)... 

Synthetic Charcoal Carbosieve Alkyl mercury compounds Methyl formate... 

Treatment of the mercurio ketone with Ni(CO)4 results in a symmetrical coupling with incorporation of one molecule of carbon monoxide to give a triketone presumably via a 3-nickel substituted ketone Eq. (28) [34], This symmetrical coupling reaction is general for alkyl mercury compounds. 

Mercury poisoning is usually treated with chelating agents such as dimercaprol or penicillamine, or hemodialysis may be used in severe cases. These help to decrease the body burden of mercury. However, chelating agents are not very effective after alkyl mercury exposure. 

An understanding of the environmental fate of these elements is necessary in the total assessment of associated health risks. Mercury is known to cycle between the geosphere and biosphere (35). Once in the hydrosphere, it can be converted by sediment flora into highly toxic methylmercury whereupon it is incorporated into aquatic life and ultimately accumulates in human food chains (31). Limited bacterial conversion of inorganic to organic mercury has been shown to occur in soil humus (36) and in animal tissue as well (37). There is no evidence that alkylated mercury is generated from coal combustion directly if it did it would probably be dissociated to the elemental form (14). 

A number of one-alkyl mercury-for-mercury exchanges, proceeding by mechanism SE1, have been considered in Chapter 4, Sections 1.1 (p. 23) and 1.2 (p. 25). 

Fig. 1. A possible reaction path and energy profile for the uncatalysed one-alkyl mercury-for-...

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