Tetraethyllead synthesis

Ethyl Chloride. Previously a significant use for industrial ethanol was the synthesis of ethyl chloride [75-00-3] for use as an intermediate in producing tetraethyllead, an antiknock gasoline additive. Ethanol is converted to ethyl chloride by reaction with hydrochloric acid in the presence of aluminum or zinc chlorides. However, since about 1960, routes based on the direct addition of hydrochloric acid to ethylene or ethane have become more competitive (374,375). 

Kharasch, M.S., Jensen, E.V., and Weinhouse, S., Alkylation reactions of tetraethyllead. A new synthesis of ethyldichloroarsine and related compounds,... 

Diethyllead decomposes at the synthesis temperature, forming tetraethyllead and metallic lead. The main reaction is accompanied by some by-processes E.g., we find triethyllead, which can easily turn into a dimer, hexaethyldilead. 

Tetraethyllead can be synthesised in reactors of various construction and various volume. The process comprises two stages (Fig. 94) the synthesis of tetraethyllead its distillation from the reactive mixture with water vapour. 

The disadvantages of the chemical technique of tetraethyllead production are the low degree of reactant transformation (75% of the lead does not enter the reaction) and secondary formation of sodium chloride. Besides, it is very problematic to extract tetraethyllead out of the spongelike mass, the mixture of lead and sodium alloy and sodium chloride completely. The process is periodic and hence difficult to automate. Electrochemical techniques for the synthesis of tetraethyllead seem to be more promising in this aspect. 

The overall reaction that takes place in the electrochemical synthesis of tetraethyllead is the following ... 

Fig. 95. Production diagram of tetraethyllead by electrolysis of complex salts 1 -4 - synthesis apparatuses 5 - electrolyser 6 - trap 7 - apparatus for decomposing sodium amalgam...

As was mentioned in Section 1, the first synthesis of an organolead compound was reported by Lowig 210>211), who synthesized tetraethyllead by the reaction of a sodium-lead alloy with ethyl iodide. Some 35 years later, Polis 247,248) prepared the first aryl lead derivative by the reaction of bromobenzene with a sodium-lead alloy. Since 1923, the sodium-lead alloy-ethyl chloride reaction has been used for the commercial production of tetraethyllead. A similar reaction has also been used for the commercial production of tetramethyllead since 1960. The sodium-lead alloy-alkyl chloride reaction is discussed in Section 6. 

Of course, several totally new processes have been suggested for tetraethyllead, and especially, for tetramethyllead and methyl-containing mixtures. These processes are discussed under General Methods of Synthesis and "Tetramethyllead . 

Processes analogous to the well-known electrochemical synthesis of tetraethyllead (Et4Pb) from sacrificial Pb electrodes have been described for Sb and Bi. EtjBi is formed in good yields (94% based on the current passed) when an aqueous solution of NaBEt4 is oxidized at a Bi anode . If the anode material is changed to Sb, EtjSb is formed in moderate yields based on the current passed (25-50% dependent on the current density) . The lower yields at the Sb anode were ascribed to passivation of the electrode . 

The lead which separates may be fully utilized in the synthesis of tetraethyllead by adding an organocadmium compound and ethyl iodide to the reaction mixture. The essential step in this multistage process clearly is ethylation of lead by cadmium diethyl ... 

Ziegler and his co-workers have described a synthesis specially designed for tetraethyllead.245,480 It starts from triethylaluminum the complex NaF 2A1(C2H5)3 or Na[R3AlC2H5] (both good conductors) is electrolyzed at a lead anode, then giving tetraethyllead readily in quantitative yield. 

Sodium is used in the manufacture of many highly reactive sodium compounds and tetraethyllead, as a reducing agent in organic synthesis, and as a catalyst in the production of synthetic rubber. It is also used in making sodium lamp and photovoltaic cells. 

The vinyl compounds are thermally more stable than the allyl derivatives. For a critical review up to 1959 see Kaesz and Stone 131). Several investigators are engaged in the synthesis and reactions of the vinyllead compounds (Table V). Tetravinyllead, first synthesized in 1959, can be distilled under vacuum and is colorless but less stable than tetraethyllead. The vinyllead grouping is more easily cleaved than the Pb—C bond in saturated organolead compounds. 

From Lead Compounds and Grignard Compounds. The most common laboratory method for synthesis of tetraethyllead is the reaction of a lead(ll) halide, usually PbCl2, with a Grignard reagent in dry ether according to the general equation ... 

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