Sec-Butyllithium
Chemical compound
From Wikipedia, the free encyclopedia
sec-Butyllithium is an organometallic compound with the formula CH3CHLiCH2CH3, abbreviated sec-BuLi or s-BuLi. This chiral organolithium reagent is used as a source of sec-butyl carbanion in organic synthesis.[2]
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| Names | |
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| IUPAC name
sec-Butyllithium | |
| Systematic IUPAC name
Butan-2-yllithium | |
| Identifiers | |
3D model (JSmol) |
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| 3587206 | |
| ChemSpider | |
| ECHA InfoCard | 100.009.026 |
| EC Number |
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PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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| Properties | |
| C4H9Li | |
| Molar mass | 64.06 g·mol−1 |
| Reacts | |
| Acidity (pKa) | 51 |
| Hazards[1] | |
| GHS labelling: | |
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| Danger | |
| H250, H260, H314 | |
| P210, P222, P223, P231, P231+P232, P233, P260, P264, P264+P265, P280, P301+P330+P331, P302+P335+P334, P302+P361+P354, P304+P340, P305+P354+P338, P316, P317, P321, P363, P370+P378, P402+P404, P405, P501 | |
| Safety data sheet (SDS) | Fisher MSDS |
| Related compounds | |
Related organolithium reagents |
n-butyllithium tert-butyllithium |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Synthesis
Properties
Physical properties
sec-Butyllithium is a colorless viscous liquid.[2][4] Using mass spectrometry, it was determined that the pure compound has a tetrameric structure.[5] It also exists as tetramers when dissolved in organic solvents such as benzene, cyclohexane or cyclopentane.[4] The cyclopentane solution has been detected with 6Li-NMR spectroscopy to have a hexameric structure at temperatures below −41 °C.[6] In electron-donating solvents such as tetrahydrofuran, there exists an equilibrium between monomeric and dimeric forms.[7]
Chemical properties
The carbon-lithium bond is highly polar, rendering the carbon basic, as in other organolithium reagents. Sec-butyllithium is more basic than the primary organolithium reagent, n-butyllithium. It is also more sterically hindered. sec-BuLi is employed for deprotonations of particularly weak carbon acids where the more conventional reagent n-BuLi is unsatisfactory. It is, however, so basic that its use requires greater care than for n-BuLi. For example diethyl ether is attacked by sec-BuLi at room temperature in minutes, whereas ether solutions of n-BuLi are stable.[2]
The compound decomposes slowly at room temperature and more rapidly at higher temperatures, giving lithium hydride and a mixture of butenes.[8][9]
Applications
Many transformations involving sec-butyllithium are similar to those involving other organolithium reagents.
In combination with sparteine as a chiral auxiliary, sec-butyllithium is useful in enantioselective deprototonations.[10] It is also effective for lithiation of arenes.[11]