organolithiumühend

Organolithium compounds are a class of organometallic compounds containing a carbon-lithium bond. They are characterized by the highly polar nature of the carbon-lithium bond, which makes the carbon atom nucleophilic and basic. This reactivity makes organolithium reagents very useful in organic synthesis, particularly for the formation of new carbon-carbon bonds.

The preparation of organolithium compounds typically involves the reaction of an organohalide with an alkali metal, most commonly lithium metal. For example, n-butyllithium can be synthesized by reacting n-butyl bromide with lithium metal in an ethereal solvent. Alternatively, they can be prepared by the deprotonation of a carbon acid using a strong base, such as an alkyllithium. For instance, phenyllithium can be formed by treating benzene with n-butyllithium.

Organolithium reagents are highly reactive and often pyrophoric, meaning they can ignite spontaneously in air. Therefore, they must be handled under an inert atmosphere, such as nitrogen or argon, and in anhydrous solvents to prevent decomposition and unwanted side reactions. Common solvents include diethyl ether, tetrahydrofuran (THF), and hexane.

The reactivity of organolithium compounds stems from the partial positive charge on the lithium atom and the partial negative charge on the carbon atom. This polarity allows the carbanionic carbon to readily attack electrophilic centers, such as carbonyl groups, epoxides, and alkyl halides. This nucleophilic addition is a fundamental reaction in organic chemistry, enabling the synthesis of a wide variety of complex molecules. Examples include the Grignard reaction (though Grignard reagents are magnesium-based, the principle of nucleophilic attack is similar) and various coupling reactions.