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| Names | |
|---|---|
| Preferred IUPAC name tert-Butyllithium[citation needed] | |
| Identifiers | |
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3D model (JSmol) | |
| 3587204 | |
| ChemSpider |
|
| ECHA InfoCard | 100.008.939 |
| EC Number |
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| UN number | 3394 |
| |
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| Properties | |
| LiC 4H 9 | |
| Molar mass | 64.055 g mol−1 |
| Appearance | Colorless solid |
| Density | 660 mg cm−3 |
| Boiling point | 36 to 40 °C (97 to 104 °F; 309 to 313 K) |
| Reacts | |
| Acidity (pKa) | 45–53 |
| Hazards | |
| GHS labelling: | |
     | |
| Danger | |
| H225,H250,H260,H300,H304,H310,H314,H330,H336,H411 | |
| P210,P222,P223,P231+P232,P370+P378,P422 | |
| NFPA 704 (fire diamond) | |
| Flash point | −6.6 °C (20.1 °F; 266.5 K) |
| Related compounds | |
Related compounds | n-Butyllithium sec-Butyllithium |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
tert-Butyllithium is achemical compound with theformula (CH3)3CLi. As anorganolithium compound, it has applications inorganic synthesis since it is a strongbase, capable ofdeprotonating many carbon molecules, includingbenzene.tert-Butyllithium is available commercially as solutions in hydrocarbons (such aspentane); it is not usually prepared in the laboratory.
tert-Butyllithium is produced commercially by treatingtert-butyl chloride withlithium. Its synthesis was first reported byR. B. Woodward in 1941.[1]
Like other organolithium compounds,tert-butyllithium is acluster compound. Whereasn-butyllithium exists both as a hexamer and a tetramer,tert-butyllithium exists exclusively as a tetramer with acubane structure. Bonding in organolithium clusters involvessigma delocalization and significant Li−Li bonding.[2] Despite its complicated structure,tert-butyllithium is usually depicted in equations as a monomer.
The lithium–carbon bond intert-butyllithium is highly polarized, having about 40 percentionic character. The molecule reacts like acarbanion, as is represented by these tworesonance structures:[3]
tert-Butyllithium is renowned for deprotonation of carbon acids (C-H bonds). One example is the double deprotonation ofallyl alcohol.[4] Other examples are the deprotonation ofvinyl ethers.[5][6][7]
In combination withn-butyllithiium,tert-butylllithium monolithiatesferrocene.[8]tert-Butyllithium deprotonatesdichloromethane:[9]
Similar ton-butyllithium,tert-butyllithium can be used forlithium–halogen exchange reactions.[10][11]
To minimize degradation by solvents, reactions involvingtert-butyllithium are often conducted at very low temperatures in special solvents, such as theTrapp solvent mixture.
More so than other alkyllithium compounds,tert-butyllithium reacts withethers.[2] Indiethyl ether, thehalf-life oftert-butyllithium is about 60 minutes at 0 °C. It is even more reactive towardtetrahydrofuran (THF); the half-life in THF solutions is about 40 minutes at −20 °C.[12] Indimethoxyethane, the half-life is about 11 minutes at −70 °C[13]
In this example, the reaction oftert-butyllithium with (THF) is shown:
tert-butyllithium is apyrophoric substance, meaning that it spontaneously ignites on exposure to air.Air-free techniques are important so as to prevent this compound from reacting violently with oxygen and moisture:
The solvents used in common commercial preparations are themselves flammable. While it is possible to work with this compound usingcannula transfer, traces oftert-butyllithium at the tip of the needle or cannula may ignite and clog the cannula with lithium salts. While some researchers take this "pilot light" effect as a sign that the product is "fresh" and has not degraded due to time or improper storage/handling, others prefer to enclose the needle tip or cannula in a short glass tube, which is flushed with an inert gas and sealed at each end with septa.[14] Serious laboratory accidents involvingtert-butyllithium have occurred. For example, in 2008 a staff research assistant,Sheharbano Sangji, in the lab ofPatrick Harran[15] at theUniversity of California, Los Angeles, died after being severely burned by a fire ignited bytert-butyllithium.[16][17][18]
Large-scale reactions may lead to runaway reactions, fires, and explosions whentert-butyllithium is mixed with ethers such as diethyl ether, and tetrahydrofuran. The use of hydrocarbon solvents may be preferred.
