sec-Butyllithium

sec-Butyllithium

Skeletal formula of sec-butyllithium Skeletal formula of sec-butyllithium
Skeletal formula of tetrameric sec-butyllithium Skeletal formula of tetrameric sec-butyllithium
Names
IUPAC name sec-Butyllithium
Systematic IUPAC name Butan-2-yllithium
Identifiers
CAS Number	598-30-1 checkY
3D model (JSmol)	Interactive image Interactive image
Beilstein Reference	3587206
ChemSpider	10254345 checkY
ECHA InfoCard
EC Number	209-927-7
E number
PubChem CID	102446
UNII	5YV3GII1TB checkY
CompTox Dashboard (EPA)	{{#property:P3117}}
InChI InChI=1S/C4H9.Li/c1-3-4-2;/h3H,4H2,1-2H3; checkY Key: VATDYQWILMGLEW-UHFFFAOYSA-N checkY InChI=1/C4H9.Li/c1-3-4-2;/h3H,4H2,1-2H3;/rC4H9Li/c1-3-4(2)5/h4H,3H2,1-2H3 Key: VATDYQWILMGLEW-MHILWDCKAX
SMILES [Li]C(C)CC CC([Li])CC
Properties
Chemical formula	C4H9Li
Molar mass	64.06 g·mol−1
Solubility in water	Reacts
Acidity (pKa)	51
Hazards
GHS labelling:
Pictograms	GHS02: FlammableGHS05: Corrosive
Signal word	Danger
Hazard statements	H250, H260, H314
Precautionary statements	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). checkY verify (what is checkY☒N ?) Infobox references

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.

Synthesis

sec-BuLi can be prepared by the reaction of sec-butyl halides with lithium metal:

File:Sec Butyllithium synthesis 01.svg

Properties

Physical properties

sec-Butyllithium is a colorless viscous liquid. Using mass spectrometry, it was determined that the pure compound has a tetrameric structure. It also exists as tetramers when dissolved in organic solvents such as benzene, cyclohexane or cyclopentane. The cyclopentane solution has been detected with ⁶Li-NMR spectroscopy to have a hexameric structure at temperatures below −41 °C. In electron-donating solvents such as tetrahydrofuran, there exists an equilibrium between monomeric and dimeric forms.

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.

The compound decomposes slowly at room temperature and more rapidly at higher temperatures, giving lithium hydride and a mixture of butenes.

File:Sec Butyllithium decomposition.svg

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. It is also effective for lithiation of arenes.