N-Butyllithium

N-Butyllithium (n-BuLi) is an organolithium reagent used in synthetic chemistry. It is a colorless or light yellow solution when dissolved in hydrocarbon solvents such as hexane or heptane. N-Butyllithium is highly reactive and functions as a strong base and nucleophile in organic synthesis. It is commonly used for the deprotonation of acidic hydrogen atoms in organic molecules, allowing for the formation of carbon-lithium bonds and subsequent nucleophilic addition reactions.

Properties

N-Butyllithium exists as a cluster in solution and in the solid state, a characteristic common to many organolithium compounds. It is extremely pyrophoric and reacts violently with water, producing butane and lithium hydroxide. Due to its high reactivity, n-BuLi must be handled under an inert atmosphere in a dry solvent.

Synthesis

N-Butyllithium is typically synthesized by the reaction of butyl chloride with lithium metal in a hydrocarbon solvent. This process involves a two-phase reaction, where the lithium metal is dissolved in a non-polar solvent and reacts with the butyl chloride to produce n-BuLi and lithium chloride (LiCl) as a by-product.

Applications

N-Butyllithium is widely used in organic synthesis for various applications:

• Deprotonation: It is employed to deprotonate acidic protons from molecules, generating carbanions which can act as nucleophiles.
• Anionic polymerization: n-BuLi serves as an initiator for the anionic polymerization of dienes, such as butadiene and isoprene, leading to the production of synthetic rubbers.
• Halogen-Lithium exchange: It is used in halogen-lithium exchange reactions, which are useful for the synthesis of organolithium compounds from organic halides.
• Metalation: The reagent can effect metalation, where a hydrogen atom is replaced by a lithium atom, facilitating further functionalization of the molecule.

Safety

Due to its strong reactivity, especially with water and air, n-BuLi must be handled with extreme caution. Appropriate safety measures, including the use of an inert atmosphere and dry solvents, are essential to prevent uncontrolled reactions.

See Also

• Organolithium reagent
• Synthetic chemistry
• Deprotonation
• Anionic polymerization