Organolithium Compounds

compounds that contain a carbon-lithium bond, R—Li. Aliphatic organolithium compounds are colorless crystalline substances (R = CH₃, C₂H₅, tert-C₄H₉), nondistillable viscous liquids (R = n-C₃H₇— n-C₁₂H₂₅), or low-melting waxlike substances (R = higher alkyls) that are readily soluble in hydrocarbons (except CH₃Li) and ethers. Aromatic organolithium compounds are white or yellowish crystalline substances, insoluble in hydrocarbons but soluble in ethers.

Organolithium compounds are usually produced by the reaction of metallic lithium and chlorous or bromous alkyls or aryls in a hydrocarbon or ether medium:

RX + 2Li → RLi + LiX

The solutions produced are used directly in the synthesis of various classes of compounds. Solutions of organolithium compounds that do not contain a lithium halide are formed by heating lithium with organomercury compounds (also in a hydrocarbon medium). Individual organolithium compounds can be extracted from these solutions.

Organolithium compounds take part in the same reactions as organomagnesium compounds but considerably surpass them in reactivity. Organolithium compounds are extremely sensitive to the action of oxygen, moisture, and carbon dioxide; therefore, all operations carried out with them require an atmosphere of dry inert gas (nitrogen or argon). With lithium bromide and ether, organolithium compounds form complexes of the type 2RLi. LiBr. (C₂H₅)₂O.

Organolithium compounds are widely used in organic synthesis, particularly in those cases where the corresponding Grignard reagent is insufficiently active; in industry, these compounds serve as catalysts in the manufacture of butadiene and isopropene rubbers.

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