Chemistry:Tert-Butyllithium

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tert-Butyllithium
TBuLitetramer.svg
Skeletal formula of tert-butyllithium with all implicit hydrogens shown, and partial charges added
Tert-butyllithium-tetramer-from-xtal-3D-bs-A.png
Names
Preferred IUPAC name
tert-Butyllithium[citation needed]
Identifiers
3D model (JSmol)
3587204
ChemSpider
EC Number
  • 209-831-5
UN number 3394
Properties
LiC4H9
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 pictograms GHS02: Flammable GHS05: Corrosive GHS07: Harmful GHS08: Health hazard GHS09: Environmental hazard
GHS Signal word DANGER
H225, H250, H260, H300, H304, H310, H314, H330, H336, H411
P210, P222, P223, P231+232, P370+378, P422
NFPA 704 (fire diamond)
Flammability code 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g. propaneHealth code 4: Very short exposure could cause death or major residual injury. E.g. VX gasReactivity code 4: Readily capable of detonation or explosive decomposition at normal temperatures and pressures. E.g. nitroglycerinSpecial hazard W: Reacts with water in an unusual or dangerous manner. E.g. sodium, sulfuric acidNFPA 704 four-colored diamond
4
4
4
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).
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Infobox references

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 hydrocarbon solutions; 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]

Tert-Butyllithium, Mesomerie.svg

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]

H
2CCl
2 + RLi → HCCl
2Li + 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:

Zersetzung THF tert-Butyllithium1.svg
Zersetzung THF tert-Butyllithium2.svg

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.

See also

  • Sheri Sangji case

References

  1. ↑ Bartlett, Paul D.; C. Gardner Swain; Robert B. Woodward (1941). "t-Butyllithium". J. Am. Chem. Soc. 63 (11): 3229–3230. doi:10.1021/ja01856a501. 
  2. ↑ 2.0 2.1 Elschenbroich, C. (2006). Organometallics. Weinheim: Wiley-VCH. ISBN 978-3-527-29390-2. 
  3. ↑ K. P. C. Vollhardt, N. E. Schore (1999). "Organometallic reagents: sources of nucleophilic carbon for alcohol synthesis". Organic Chemistry : Structure And Function, 3rd edition. 
  4. ↑ 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. 
  5. ↑ John A. Soderquist (1990). "Acetyltrimethylsilane". Organic Syntheses 68: 25. doi:10.15227/orgsyn.068.0025. 
  6. ↑ M. A. Tschantz, L. E. Burgess, A. I. Meyers (1996). "4-Ketoundecanoic Acid". Organic Syntheses 73: 215. doi:10.15227/orgsyn.073.0215. 
  7. ↑ 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. 
  8. ↑ 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. 
  9. ↑ Matteson, Donald S.; Majumdar, Debesh (1983). "Homologation of Boronic Esters to α-Chloro Boronic Esters". Organometallics 2 (11): 1529–1535. doi:10.1021/om50005a008. 
  10. ↑ 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. 
  11. ↑ 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. 
  12. ↑ 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. 
  13. ↑ 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. 
  14. ↑ Errington, R. M. (1997) (Google Books excerpt). Advanced practical inorganic and metalorganic chemistry. London: Blackie Academic & Professional. pp. 47–48. ISBN 978-0-7514-0225-4. https://books.google.com/books?id=yI_mq_mCf2AC&pg=PA47. 
  15. ↑ "Harran Lab: UCLA". http://faculty.chemistry.ucla.edu/institution/personnel?personnel_id=552980. 
  16. ↑ Jyllian Kemsley (2009-01-22). "Researcher Dies After Lab Fire". Chemical & Engineering News. http://pubs.acs.org/cen/news/87/i04/8704news1.html. 
  17. ↑ 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. http://pubs.acs.org/cen/science/87/8731sci1.html. 
  18. ↑ Los Angeles Times, 2009-03-01



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