Tetramethyllead

The second set of experiments was carried out in 1929 by Paneth. The decomposition of tetramethyllead was carried out in such a way that the decomposition products were carried by a flow of inert gas over a film of lead metal. The lead was observed to disappear with re-formation of tetramethyllead. The conclusion was reached that methyl radicals must exist long enough in the gas phase to be transported from the point of decomposition to the lead film, where they were reconverted to tetramethyllead. 

An exchange reaction between bis(trifluorometbyl)mercury and tetrame-thylleud gives trimethyl(mfluoromethyl)plumbane [23] (equation 17) This plum-bane can also be prepared via the reaction of tetramethyllead with tnfluoromethyl radicals produced in a radio-frequency discharge of C2F [24]... 

The structure was solved by the multiple isomorphous replacement technique using four heavy atom derivatives uranyl acetate, plati-nous chloride, tetramethyllead acetate, and p-chloromercury benzoate. All four derivatives gave interpretable heavy atom Patterson syntheses. The heavy atom sites could be correlated between the de-... 

Temperature programming packed-capillary and open capillary HTLC-ICP-MS (up to 200 °C) has been reported [738]. //.HTLC-ICP-MS instrumental coupling has been applied to organotin (tetraethyltin, tributyltin chloride and triphenyltin chloride) and organolead (tetramethyllead and tetraethyllead) compounds [756]. HTLC-ICP-MS can be used for the determination of organometallic compounds at low concentrations. The observed limit of detection (LOD) was 5pg for Pb in... 

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

Gething I. 1975. Tetramethyllead absorption A report of a human exposure to a high level of... 

On the other hand, the presence of a short-lived free radical was confirmed first from an elegant experiment in 1929 by Paneth and Hofeditz [44], although the existence of paramagnetic species was pointed out in the middle of the 19th century by Faraday [45]. When tetramethyllead was thermolyzed, a methyl radical was postulated to be formed as the reaction intermediate (Eq. 2)... 

T etrafluoromethane Tetrahydrofuran Tetramethyllead (as Pb) Tetramethylsuccinonitrile T etranitromethane Thionyl chloride Thiram Toluene... 

The classical large-scale method for preparation of tetraethyllead and tetramethyllead is by reaction of alkyl halide with sodium/lead alloy (composition Pb Na 1/1 )38. The product is isolated by steam distillation and yields are high ... 

Electrochemical synthesis was utilized to prepare labeled compounds. Tetramethyllead labeled with 14C was prepared in a double compartment cell in DMF with NaClC>4, by electrolyzing 14CH3l on lead electrodes. The method is reported as superior to transmet-allation with methylmagnesium halide. It is also possible to incorporate lead isotopes. 2i°Pb2+ ions were deposited on a Cu foil and the latter was used as a sacrificial electrode in solutions of CH3I. The yield of labeled tetramethyllead was 85%65. Synthesis of 210Pb-labeled chlorotrimethylplumbane was also described66. 

Samples for determination of ionic alky Head species in marine fauna were homogenized in the presence of salts and the alkyllead component was extracted with toluene and oxidized with HN03. Determination was by DPASV115. A method based on oxidation on Hg electrode has been described116 for analysis of alkylleads in gasoline. Alkylation of Hg is involved, of course, but as an oxidation the method does not suffer from the background of atmospheric oxygen. The peak potentials Ev for oxidation of tetramethyllead and tetraethyllead on various cathodes are well resolved (Table 5). 

TABLE 5. Peak potentials Ep for oxidation of tetramethyllead and tetraethyllead on three different electrodes in AN 0.1 M EtaNCKV at 20°C, Ag AgCl reference, calibrated at +0.38 V vs 10 3 ferrocene116... 

The oxidation mechanism of tetraethyllead and tetramethyllead on mercury cathodes has already been mentioned120. Studies under a short pulse on DME in dichloromethane indicate a single ET ... 

The initial pathway is the same for tetramethyllead. However, under prolonged electrolysis additional reactions are observed with hexamethyldilead, namely ... 

Further reaction of Ph3P+ and Hg contributes the second ET for the overall two-electron oxidation. This was studied in detail for oxidations of tetraphenyllead, tetraethyllead and tetramethyllead at mercury electrodes in dichloromethane. The rationale of the mechanisms proposed above is based on the following observations122. 

Maximum yield was obtained when the applied voltage was 13.1 V, the cathode surface area was 4 cm2 and the total CH3I concentration was 35.2 pmol. The C-14 labelled tetramethyllead was isolated by the extraction procedures developed for the Grignard route (vide supra). It was next converted to 14CH3(CH3)2PbCl by controlled oxidation 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. 

Wei and collaborators180 studied the long-range deuterium isotope effects on the proton chemical shifts of tetramethyllead and chlorotrimethylplumbane. The perdeuterated analogues of these organolead compounds were generated in situ by reaction of equimolar amounts of (CD3)3SnCl and (CH3)4Pb in methanol-d, in equation 118. 

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