Trimethyllead

Aria F, Yamamura Y. 1990. Excretion of tetramethyllead, trimethyllead and inorganic lead after injection of tetramethyllead to rabbits. Ind Health 28 63-76. 

Trimethyllead hydroxides or methoxides, sometimes used in direct reactions with acetylenic derivatives for the preparation of alkynylplumbanes, are very suitable reagents176 ... 

Trimethyllead diazoacetic acid ethyl ester reacts with activated alkenes or acetylenes to provide organolead pyrazoles or pyrazolines197 ... 

It is noteworthy to add that potassium borohydride and trimethyllead chloride, upon reaction in liquid ammonia, first produce trimethyllead borohydride which, on distillation, gives H3B NH3, ammonia and trimethylplumbane245 ... 

The methyl-[14C]-dimethyltin chloride was used to compare the performance of packed and megabore capillary columns in a gas chromatographic analysis for separating mixtures of a carbon-14 labelled trimethyllead chloride, tetramethyltin, dimethyltin dichloride and methyltin trichloride. The megabore column was able to separate all four methyltin compounds quickly, i.e., before the tetramethyltin decomposed into trimethyltin chloride and dimethyltin dichloride (equation 47), a reaction which did occur on the packed columns. Thus, the megabore column enabled the determination of the precise distribution of the various methyltin compounds in an environmental sample. The packed columns, on the other hand, could not separate dimethyltin dichloride and the methyltin trichloride and allowed significant decomposition of the tetramethyltin during the 15 minutes the analysis required. 

The C-14 labelled trimethyllead cation was recovered from the aqueous phase by adding dimethyldithiocarbamate (DMDTC) in hexane to form a trimethyllead-DMDTC complex. After the latter had been purified on preparative polyamide-6 TLC plates, the (14CH3)(CH3)2PbCl was obtained by treating the pure C-14 labelled (CH3)3Pb-DMDTC complex with HC1. 

The lead-210 labelled chlorotrimethylplumbane was prepared by adding HC1 to the tetramethyllead-210 at 0 °C. The crude product was treated with the complexometric agent dimethyldithiocarbamate and the trimethyllead-210-DMDTC complex was purified by preparative TLC. Addition of HC1 to the pure lead-210 labelled Me3Pb-DMDTC complex yielded the desired lead-210 labelled Me3PbCl. 

A mixture of Me3210PbCl and 210Pb(NO3)2 was used to study the rate of ionic trimethyl-lead uptake by exposed plant surfaces. More specifically, the mean cumulative activity of the lead toxicants transferred across tomato cuticle was measured daily over a six-day period. Reversed-phase HPLC was used to separate and identify the lead species crossing the plant cuticle. It was found that appreciably more trimethyllead(I) (75% of the theoretical) than inorganic lead(II) (39%) was transferred. The apparent rate constants derived from the first-order plot of time in days versus the difference in observed activity were 0.0788 and 0.0346 day-1 for transfer of the trimethyllead(I) and inorganic lead(II), respectively. 

A blank and also a sterile solution containing Pb2+ of methyllead compounds showed no Pb content in the methanolic solution after the same treatment. The author concluded that Me4Pb was produced in the biomethylation of Pb2+ by bacteria123. Thompson and Crerar122 also observed that about 0.03% of lead as Pb(NC>3)2 underwent methylation and trimethyllead acetate, (CH3)3PbOAc, was methylated nearly quantitatively in incubation experiments with marine sediments from the British Columbia coastline. 

Some claims have, however, been made that the methylation of lead was not biologically mediated. In 1980, Craig126 studied the methylation of trimethyllead acetate in a lake sediment (Lake Minetonka, Minn., U.S.A.), and concluded that it is not necessary to invoke a biological route to the methylation and that the results in this case can be explained entirely by a disproportionation process126. Craig and Wood also proposed an abiotic methylation route of lead127. 

Forsyth and coworkers116 postulated that the ubiquity of trimethyllead in ducks can be accounted for if the methylation of Pb2+ was environmentally mediated. 

Chau and coworkers133 investigated the bioaccumulation of alkyllead compounds from water and from contaminated sediments by freshwater mussels, Elliptio complanata. Higher levels of trimethyllead than triethyllead species were accumulated after the same exposure period. In vivo transformation of the trialkyllead species by a series of dealkylation reactions giving dialkyllead and inorganic lead(II) species appears to take place. Rates of accumulation are higher for the more contaminated sediments133. 

As shown before in Section RLE., the toxic effects upon the freshwater alga, Pote-rioochromonas malhamensis, of the trimethyllead compound (Mc3 PbAc) was thirtyfold larger than that of the inorganic lead compound (PbClp)82. 

As mentioned before, trimethyllead was found by Wong132 to be dealkylated to form dimethyllead and inorganic lead(II) by freshwater algae. 

Tetraethyllead was used in the past as an antiknock agent in gasoline, but it has been phased out in most countries. Alkyllead compounds have a detergent-like activity on liposomes and black lipid membranes [232], Tributyllead destroys planar lipid membranes at lower concentrations than tripropyllead, which is again more effective than triethyl- and trimethyllead [232]. Inorganic lead compounds like lead acetate and lead nitrate were effective only at twice as high concentrations [232]. 

The procedure [16] discussed in section 13.2.2.1 for the determination of alkyllead compounds in non-saline sediments has also been applied to marine sediments. Recoveries from sediments ranged from 94% for triethyllead to 111% for trimethyllead in the range l-20pg alkyllead spiked to lg of sediment. An average standard deviation of 4% for trimethyllead and triethyllead and 15% for dialkylead compounds was obtained. 

Complex hydrides were used for reductions of organometallic compounds with good results. Trimethyllead chloride was reduced with lithium aluminum hydride in dimethyl ether at —78° to trimethylplumbane in 95% yield [1174, and 2-methoxycyclohexylmercury chloride with sodium borohydride in 0.5 n sodium hydroxide to methyl cyclohexyl ether in 86% yield [1175]. 

The potential of transformation reactions for synthesizing a wider range of block copolymers has not been realized because either the reactions are not quantitiative or deterimental side reactions occur. Thus coupling of two propagating carbanions by one phosgene competes with the 1 1 transformation in Eq. 5-123. The anionic-to-radical transformation in Eq. 5-124 involves the formation of trimethyllead radical, which initiates homopolymerization of monomer B. 

LC50 for triethyllead LC50 for trimethyllead LC50 for dimethyllead LC50 for diethyllead MATC... 

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