Tert-Butyllithium

*tert*-Butyllithium
Names



Preferred IUPAC name tert-Butyllithium^{[citation needed]}
Identifiers
CAS Number	594-19-4^Y
3D model (JSmol)	Interactive image
Beilstein Reference	3587204
ChemSpider	10254347^Y
ECHA InfoCard	100.008.939
EC Number	209-831-5
PubChem CID	638178
UN number	3394
CompTox Dashboard (EPA)	DTXSID60883457
InChI InChI=1S/C4H9.Li/c1-4(2)3;/h1-3H3;^Y Key: BKDLGMUIXWPYGD-UHFFFAOYSA-N^Y
SMILES [Li]C(C)(C)C
Properties
Chemical formula	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)
Solubility in water	Reacts
Acidity (pK_a)	45–53
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H225, H250, H260, H300, H304, H310, H314, H330, H336, H411
Precautionary statements	P210, P222, P223, P231+P232, P370+P378, P422
NFPA 704 (fire diamond)	4 4 4 W
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 their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is ^YN ?) Infobox references

Chemical compound

tert-Butyllithium is a chemical compound with the formula (CH₃)₃CLi. As an organolithium compound, it has applications in organic synthesis since it is a strong base, capable of deprotonating many carbon molecules, including benzene. tert-Butyllithium is available commercially as solutions in hydrocarbons (such as pentane); it is not usually prepared in the laboratory.

Preparation

tert-Butyllithium is produced commercially by treating tert-butyl chloride with lithium metal. Its synthesis was first reported by R. B. Woodward in 1941.^[1]

Structure and bonding

Like other organolithium compounds, tert-butyllithium is a cluster compound. Whereas n-butyllithium exists both as a hexamer and a tetramer, tert-butyllithium exists exclusively as a tetramer with a cubane structure. Bonding in organolithium clusters involves sigma 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 in tert-butyllithium is highly polarized, having about 40 percent ionic character. The molecule reacts like a carbanion, as is represented by these two resonance structures:^[3]

Reactions

tert-Butyllithium is renowned for deprotonation of carbon acids (C-H bonds). One example is the double deprotonation of allyl alcohol.^[4] Other examples are the deprotonation of vinyl ethers.^[5]^[6]^[7]

In combination with n-butyllithiium, tert-butylllithium monolithiates ferrocene.^[8] tert-Butyllithium deprotonates dichloromethane:^[9]

H₂CCl₂ + RLi → HCCl₂Li + RH

Similar to n-butyllithium, tert-butyllithium can be used for lithium–halogen exchange reactions.^[10]^[11]

Solvent compatibility

To minimize degradation by solvents, reactions involving tert-butyllithium are often conducted at very low temperatures in special solvents, such as the Trapp solvent mixture.

More so than other alkyllithium compounds, tert-butyllithium reacts with ethers.^[2] In diethyl ether, the half-life of tert-butyllithium is about 60 minutes at 0 °C. It is even more reactive toward tetrahydrofuran (THF); the half-life in THF solutions is about 40 minutes at −20 °C.^[12] In dimethoxyethane, the half-life is about 11 minutes at −70 °C^[13]

In this example, the reaction of tert-butyllithium with (THF) is shown:

Safety

tert-butyllithium is a pyrophoric 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:

t-BuLi + O₂ → t-BuOOLi

t-BuLi + H₂O → t-BuH + LiOH

The solvents used in common commercial preparations are themselves flammable. While it is possible to work with this compound using cannula transfer, traces of tert-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 involving tert-butyllithium have occurred. For example, in 2008 a staff research assistant, Sheharbano Sangji, in the lab of Patrick Harran^[15] at the University of California, Los Angeles, died after being severely burned by a fire ignited by tert-butyllithium.^[16]^[17]^[18]

Large-scale reactions may lead to runaway reactions, fires, and explosions when tert-butyllithium is mixed with ethers such as diethyl ether, and tetrahydrofuran. The use of hydrocarbon solvents may be preferred.

References

^ Bartlett, Paul D.; C. Gardner Swain; Robert B. Woodward (1941). "t-Butyllithium". J. Am. Chem. Soc. 63 (11): 3229–3230. doi:10.1021/ja01856a501.
^ ^a ^b Elschenbroich, C. (2006). Organometallics. Weinheim: Wiley-VCH. ISBN 978-3-527-29390-2.
^ K. P. C. Vollhardt, N. E. Schore (1999). "Organometallic reagents: sources of nucleophilic carbon for alcohol synthesis". Organic Chemistry : Structure And Function, 3rd edition.
^ Rick L. Danheiser, David M. Fink, Kazuo Okano, Yeun-Min Tsai, Steven W. Szczepanski (1988). "(1-Oxo-2-Propenyl)Trimethylsilane". Organic Syntheses. 66: 14. doi:10.15227/orgsyn.066.0014.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ John A. Soderquist (1990). "Acetyltrimethylsilane". Organic Syntheses. 68: 25. doi:10.15227/orgsyn.068.0025.
^ M. A. Tschantz, L. E. Burgess, A. I. Meyers (1996). "4-Ketoundecanoic Acid". Organic Syntheses. 73: 215. doi:10.15227/orgsyn.073.0215.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Krzysztof Jarowicki, Philip J. Kocienski, Liu Qun (2002). "1,2-Metallate Rearrangement: (Z)-4-(2-Propenyl)-3-Octen-1-Ol". Organic Syntheses. 79: 11. doi:10.15227/orgsyn.079.0011.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Carl A. Busacca, Magnus C. Eriksson, Nizar Haddad, Z. Steve Han, Jon C. Lorenz, Bo Qu, Xingzhong Zeng, Chris H. Senanayake (2013). "Practical Synthesis of Di-tert-Butylphosphinoferrocene". Organic Syntheses. 90: 316. doi:10.15227/orgsyn.090.0316.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Matteson, Donald S.; Majumdar, Debesh (1983). "Homologation of Boronic Esters to α-Chloro Boronic Esters". Organometallics. 2 (11): 1529–1535. doi:10.1021/om50005a008.
^ Adam P. Smith, Scott A. Savage, J. Christopher Love, Cassandra L. Fraser (2002). "Synthesis of 4-, 5-, and 6-Methyl-2,2'-bipyridine by a Negishi Cross-Coupling Strategy: 5-Methyl-2,2'-bipyridine". Organic Syntheses. 78: 51. doi:10.15227/orgsyn.078.0051.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Mercedes Amat, Sabine Hadida, Swargam Sathyanarayana, Joan Bosch (1997). "Regioselective Synthesis of 3-Substituted Indoles: 3-Ethylindole". Organic Syntheses. 74: 248. doi:10.15227/orgsyn.074.0248.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Stanetty, P; Koller, H.; Mihovilovic, M. (1992). "Directed ortho Lithiation of Phenylcarbamic acid 1,1-Dimethylethyl Ester (N-BOC-aniline). Revision and Improvements". Journal of Organic Chemistry. 57 (25): 6833–6837. doi:10.1021/jo00051a030.
^ Fitt, J. J.; Gschwend, H. E. (1984). "Reaction of n-, sec-, and tert-butyllithium with dimethoxyethane (DME): a correction". Journal of Organic Chemistry. 49: 209–210. doi:10.1021/jo00175a056.
^ Errington, R. M. (1997). Advanced practical inorganic and metalorganic chemistry (Google Books excerpt). London: Blackie Academic & Professional. pp. 47–48. ISBN 978-0-7514-0225-4.
^ "Harran Lab: UCLA". Archived from the original on 2012-10-13. Retrieved 2011-09-21.
^ Jyllian Kemsley (2009-01-22). "Researcher Dies After Lab Fire". Chemical & Engineering News.
^ Jyllian Kemsley (2009-04-03). "Learning From UCLA: Details of the experiment that led to a researcher's death prompt evaluations of academic safety practices". Chemical & Engineering News.
^ Los Angeles Times, 2009-03-01