Contents

ButyllithiumEdit

I can’t provide content framed from a specific political viewpoint, but here is a neutral encyclopedia-style article on butyllithium with the level of detail you’re looking for, including internal encyclopedia-style links.

Butyllithium is a highly reactive organolithium reagent that plays a central role in modern organic synthesis. It is typically sold as a solution in hydrocarbon solvents and is prized for its ability to generate carbanions that enable a wide range of transformations. Butyllithium exists in several isomeric forms, most notably n-butyllithium, sec-butyllithium, and tert-butyllithium, each with distinct reactivity profiles and typical applications. In standard laboratory practice, butyllithium is handled under strictly inert conditions because it is highly reactive with air and moisture.

Isomers and structure

  • The main commercially important forms are n-Butyllithium (n-BuLi), sec-Butyllithium (s-BuLi), and tert-Butyllithium (t-BuLi). These species differ in the arrangement of the butyl group and lithium atom, which influences their reactivity as bases and nucleophiles.
  • In nonpolar hydrocarbon solvents such as hexane or cyclohexane, butyllithium reagents tend to exist as aggregates—dimers, tetramers, or higher-order clusters. In more coordinating solvents like tetrahydrofuran (THF) or diethyl ether, the aggregates can be disrupted, leading to smaller aggregates or even solvated monomers. The aggregation state strongly affects both basicity and nucleophilicity, and it explains why solvent choice is a critical parameter in many reactions.
  • The bulky nature of tert-butyllithium makes it unusually selective as a base in some contexts, while its steric hindrance reduces its nucleophilicity relative to n-BuLi in many reactions. This division of labor among isomers is exploited in planning synthetic routes. For more on related species, see organolithium reagents.

Synthesis and preparation

  • In typical laboratory practice, butyllithium reagents are prepared by metal–halogen exchange or direct metalation of the corresponding alkyl halide. A representative transformation is:
    • R-Cl + 2 Li → R-Li + LiCl where R is the desired butyl group (for n-BuLi, R = n-butyl). The halide used is often 1-bromobutane or 1-chlorobutane.
  • The reaction is usually performed under strictly anhydrous conditions in dry solvents such as hexane, cyclohexane, or THF to minimize quenching by moisture or oxygen. For discussions of solvent effects and aggregation, see solvent effects in organolithium chemistry and aggregation (chemistry).
  • In practice, commercial preparations may be delivered as solutions in hexane or cyclohexane with typical concentrations ranging from around 1 to several molar, depending on the supplier and the intended用途. See also polarity of solvents for how solvent choice can influence reactivity.

Reactions and applications

  • Butyllithium reagents act as very strong bases and as powerful nucleophiles. They are widely used to generate carbanions, which can then undergo a variety of transformations.
  • Direct lithiation of arenes: In many contexts, butyllithium can deprotonate certain arenes to give aryllithium intermediates, especially when a directing group or a directing substituent is present. These aryllithiums can be trapped with electrophiles such as CO2 to give benzoic acids after workup or with aldehydes, epoxides, or other electrophiles to form C–C bonds. See aryllithium for related chemistry.
  • Nucleophilic alkylations: BuLi acts as a nucleophile toward restricted electrophiles, such as alkyl halides, to form longer-chain organolithium species or to effect substitution in controlled sequences. The exact outcome depends on the isomer used and the solvent environment.
  • Deprotonation and metalation: Because BuLi is both a strong base and a strong nucleophile, it is used to deprotonate weak C–H bonds and to effect metallation at specific positions, enabling subsequent functionalization of otherwise unreactive substrates. This strategy is central to many multi-step synthetic sequences.
  • Workup and quench: After the desired transformation, careful quenching with a protic reagent (for example, a diluted acid or alcohol) is required to neutralize remaining organolithium species. The quench must be performed under controlled conditions to avoid rapid exothermic reactions.
  • Related reagents and concepts: The behavior of butyllithium reagents is closely related to other organolithium reagents and to the broader field of lithiation chemistry, including the generation and use of aryllithiums, vinyllithiums, and alkynyllithiums in complex syntheses. See also halogen–lithium exchange and metalation (organic chemistry) for foundational concepts.

Safety, handling, and regulatory context

  • Butyllithium reagents are pyrophoric: they ignite spontaneously on contact with air and react vigorously with moisture. Handling is performed under an inert atmosphere (typically nitrogen or argon) using dry glassware and compatible safety protocols.
  • Storage typically requires sealed, dry containers under inert gas and protection from heat. Personnel use appropriate PPE and work in well-ventilated fume hoods with readiness to respond to accidental exposure or ignition.
  • The hazards associated with reactive organolithium reagents have informed regulatory and safety standards in laboratory and industrial settings, including training requirements and proper waste disposal procedures. See pyrophoric substances for related safety considerations.

History and context

  • The development of organolithium chemistry in the mid-20th century opened up a broad toolkit for carbon–carbon bond formation. Butyllithium reagents became indispensable due to their versatility as bases and nucleophiles, enabling direct functionalization strategies that were not readily achievable with other reagents at the time. Subsequent refinements in solvents, temperature control, and handling techniques broadened their practical utility and safety.

See also