sec-Butyllithium
- S- butyllithium
- S- BuLi
Colorless liquid
Liquid
90 ° C ( 0.05 Torr)
Soluble in cyclohexane
Solution in cyclohexane
Risk
Based on 1.4 M solution in cyclohexane
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Sec-butyllithium (s- BuLi ) is a secondary metal-organic compound of the element lithium ( organolithium compound ). There are also the isomeric forms of n- butyllithium and tert -butyllithium. The basicity increases in the order of n-butyllithium < sec -butyl < tert- butyllithium to. s- BuLi is thus the second largest base in this series. sec -butyllithium is usually commercially available as a solution in cyclohexane. During storage, a fine lithium hydride precipitate may form; This also leads to lowering of the concentration of solutions.
Production and representation
The synthesis can be carried out by reaction of 2 -chlorobutane with elemental lithium.
Properties
Physical Properties
Sec-butyllithium is a colorless, viscous liquid. For the pure substance a tetrameric structure was detected by mass spectrometry. In nonpolar solvents such as benzene, cyclohexane or cyclopentane compound exists as a tetramer. At temperatures of -41 ° C could be detected in cyclopentane 6Li by NMR spectroscopy a hexamer. In solvents with donor properties such as tetrahydrofuran a balance between dimeric and monomeric structures exist.
Chemical Properties
S -BuLi can be used for the lithium - halogen exchange of halogenated aromatic compounds or deprotonation, for example, from amines or alcohols. With copper (I ) iodide lithium di -sec- butylcuprate be formed. Compared to n- BuLi, s -BuLi reacts faster at ambient temperature with diethyl ether and THF. The compound decomposes slowly at room temperature or at an elevated temperature and a faster lithium butene mixture of 1-butene, cis- 2-butene and trans-2- butene.
Pure s- butyl lithium is pyrophoric and burns in air with a typical red flame.
Use
The carbon- lithium bond is strongly polarized, with the result that the carbon is highly nucleophilic and basic. s- BuLi is more basic than n- BuLi and addition sterically hindered more. These two properties you can make in various syntheses advantage. It is used, for example, when only a weak CH acidity is present, and n -BuLi are no satisfactory results. In addition, s -butyllithium is used as a catalyst for technical polymerizations of isoprene, butadiene and styrene.
Safety
S- BuLi is self-igniting in air and also reacts violently with water. The reagent must be stored and handled (e.g., argon) therefore always under an inert gas.