methyllithium

Methyllithium is the simplest organolithium reagent, with the empirical formula LiCH3. This s-block organometallic compound adopts an oligomeric structure both in solution and in the solid state. This highly reactive compound, invariably used in solution with an ether as the solvent, is a reagent in organic synthesis as well as organometallic chemistry. Operations involving methyllithium require anhydrous conditions, because the compound is highly reactive towards water. Oxygen and carbon dioxide are also incompatible with MeLi. Methyllithium is usually not prepared, but purchased as a solution in various ethers.

==Synthesis== In the direct synthesis, methyl bromide is treated with a suspension of lithium in diethyl ether. 2 Li + MeBr → LiMe + LiBr The lithium bromide forms a complex with the methyllithium. Most commercially available methyllithium consists of this complex. "Low-halide" methyllithium is prepared from methyl chloride. Lithium chloride precipitates from the diethyl ether since it does not form a strong complex with methyllithium. The filtrate consists of fairly pure methyllithium. Alternatively, commercial methyllithium can be treated with dioxane to precipitate LiBr(dioxane), which can be removed by filtration. The use of halide-free vs LiBr-MeLi has a decisive effect on some syntheses.