Sodium-Lead Alloy Method

Sodium fusion may be performed using either sodium metal or a commercially available sodium-lead alloy, which contains nine parts lead and one part sodium. For safety reasons, we recommend using the sodium-lead alloy method because the alloy is easier to handle than is sodium metal and poses less potential danger during hydrolysis. 

Put the lead pellet that remains after hydrolysis of the reaction mixture in the container for heavy metals. 

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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 ... 

The initial large-scale production of tetraethyllead was based on the batchwise reaction of sodium-lead alloy with ethyl chloride. Although various details in this process have been changed over the years, the basic method remains the same for the manufacture of most of the tetraethyllead produced in the world today. 

The use of a sodium-tin alloy for the preparation of tetramethyltin preceded use of the corresponding sodium-lead alloy (64,66), but was subsequently displaced by other methods. Currently, the Direct Reaction is used to prepare dialkyltin dihalides, and generally requires an oxygen-containing solvent plus another metal as accelerator (66) ... 

Another important coupling reaction uses esters as the electron-accepting species and leads to a-hydroxy ketones (acyloin coupling). Sodium, potassium (less frequently) or sodium-potassium alloys are commonly used as electron donors in nonpolar solvents such as toluene or xylene. The first detectable reaction intermediate after the primary reductive step is the enediolate which can be trapped with tri-alkylsilyl chloride. This method is widely used to synthesize highly nucleophilic alkenes and/or protected acyloins (Scheme 12) [50, 51]. 

For example, EtCl reacts with the alloy to give tetraethyllead in 85 % yield [9]. This method is such that only one quarter of the lead is converted to lead alkyl and the remainder has to be recycled. Unfortunately, sodium-rich alloys such as Na4Pb do not react satisfactorily. Ketones, aldehydes, acetals, acid anhydrides, esters, amides, phosphoric acid esters, organosilicons, organoaluminum compounds, etc. as reaction accelerators of the alloy process have been reported [9]. For example, the reaction of EtCl at 100-120 °C in the presence of 0.1 % acetone gives tetraethyllead in 98% yield [10]. 

Trace elements can be separated from solutions of different metals by reducing a small amount of the matrix metal with sodium hydroborate (NaBH4) [82-85]. The metallic precipitate serves as a trace collector for all the elements that are electrochemically more noble than the matrix. The method has been used in the trace analysis of lead and its alloys [82-85]. 

The second method involves the addition of high heat producing extraneous oxidizers. Frequently mentioned are barium peroxide and other strong oxidizers such as lead dioxide, sodium persulfate (NagSOg) and even chlorate. Kuhne claims such additions for the aluminothermic production of numerous metals, and Cueilleron and Pascand for aluminum/titanium alloys. ... 

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