tert-Butyllithium
{{DISPLAYTITLE:tert-Butyllithium}}
{{Chembox
|Watchedfields = changed
|verifiedrevid = 470602967
|Name = tert-Butyllithium
|ImageFile1 = TBuLitetramer.svg
|ImageName1 =
|ImageFile2 = Tert-Butyllithium.png
|ImageFile_Ref = {{chemboximage|correct|??}}
|ImageName2 = Skeletal formula of tert-butyllithium with all implicit hydrogens shown, and partial charges added
|ImageFile3 = Tert-butyllithium-tetramer-from-xtal-3D-bs-A.png
|PIN = tert-Butyllithium{{Citation needed|date=October 2011}}
|Section1={{Chembox Identifiers
|CASNo = 594-19-4
|CASNo_Ref = {{cascite|correct|CAS}}
|PubChem = 638178
|ChemSpiderID = 10254347
|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
|EINECS = 209-831-5
|UNNumber = 3394
|Beilstein = 3587204
|SMILES = [Li]C(C)(C)C
|StdInChI = 1S/C4H9.Li/c1-4(2)3;/h1-3H3;
|StdInChI_Ref = {{stdinchicite|correct|chemspider}}
|StdInChIKey = BKDLGMUIXWPYGD-UHFFFAOYSA-N
|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
}}
|Section2={{Chembox Properties
|Formula = {{Chem|LiC|4|H|9}}
|MolarMass = 64.055 g mol−1
|Appearance = Colorless solid
|Density = 660 mg cm−3
|BoilingPtC = 36 to 40
|Solubility = Reacts
|pKa = 45–53
}}
|Section3={{Chembox Hazards
|GHSPictograms = {{GHS flame}} {{GHS corrosion}} {{GHS exclamation mark}} {{GHS health hazard}} {{GHS environment}}
|GHSSignalWord = DANGER
|HPhrases = {{H-phrases|225|250|260|300|304|310|314|330|336|411}}
|PPhrases = {{P-phrases|210|222|223|231+232|370+378|422}}
|NFPA-H = 4
|NFPA-F = 4
|NFPA-R = 4
|NFPA-S = W
|FlashPtC = -6.6
}}
|Section4={{Chembox Related
|OtherCompounds = n-Butyllithium
}}
}}
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. Its synthesis was first reported by R. B. Woodward in 1941.{{cite journal |last=Bartlett |first=Paul D. |author2=C. Gardner Swain |author3=Robert B. Woodward |journal=J. Am. Chem. Soc. |title=t-Butyllithium |year=1941 |volume=63 |issue=11 |pages=3229–3230 |doi=10.1021/ja01856a501|bibcode=1941JAChS..63.3229B }}
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.{{cite book |author=Elschenbroich, C. |title=Organometallics |year=2006 |publisher=Wiley-VCH |location=Weinheim |isbn=978-3-527-29390-2}} 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:{{cite book |chapter=Organometallic reagents: sources of nucleophilic carbon for alcohol synthesis |author=K. P. C. Vollhardt, N. E. Schore |title=Organic Chemistry : Structure And Function, 3rd edition |year=1999}}
Reactions
tert-Butyllithium is renowned for deprotonation of carbon acids (C-H bonds). One example is the double deprotonation of allyl alcohol.{{cite journal |doi=10.15227/orgsyn.066.0014 |title=(1-Oxo-2-Propenyl)Trimethylsilane |journal=Organic Syntheses |year=1988 |volume=66 |page=14 |last1=Danheiser |first1=Rick L. |last2=Fink |first2=David M. |last3=Okano |first3=Kazuo |last4=Tsai |first4=Yeun-Min |last5=Szczepanski |first5=Steven W. |doi-access=free |issn=2333-3553 }} Other examples are the deprotonation of vinyl ethers.{{cite journal |last=Soderquist |first=John A. |doi=10.15227/orgsyn.068.0025 |title=Acetyltrimethylsilane |journal=Organic Syntheses |year=1990 |volume=68 |page=25 |doi-access=free |issn=2333-3553 }}{{cite journal |doi=10.15227/orgsyn.073.0215 |title=4-Ketoundecanoic Acid |journal=Organic Syntheses |year=1996 |volume=73 |page=215 |last1=Tschantz |first1=M. A. |last2=Burgess |first2=L. E. |last3=Meyers |first3=A. I. |doi-access=free |issn=2333-3553 }}{{cite journal |doi=10.15227/orgsyn.079.0011 |title=1,2-Metallate Rearrangement: (Z)-4-(2-Propenyl)-3-Octen-1-Ol |journal=Organic Syntheses |year=2002 |volume=79 |page=11 |last1=Jarowicki |first1=Krzysztof |last2=Kocienski |first2=Philip J. |last3=Qun |first3=Liu |doi-access=free |issn=2333-3553 }}
In combination with n-butyllithiium, tert-butylllithium monolithiates ferrocene.{{cite journal |doi=10.15227/orgsyn.090.0316 |title=Practical Synthesis of Di-tert-Butylphosphinoferrocene |journal=Organic Syntheses |year=2013 |volume=90 |page=316 |last1=Busacca |first1=Carl A. |last2=Eriksson |first2=Magnus C. |last3=Haddad |first3=Nizar |last4=Han |first4=Z. Steve |last5=Lorenz |first5=Jon C. |last6=Qu |first6=Bo |last7=Zeng |first7=Xingzhong |last8=Senanayake |first8=Chris H. |doi-access=free |issn=2333-3553 }} tert-Butyllithium deprotonates dichloromethane:{{cite journal |doi=10.1021/om50005a008 |title=Homologation of Boronic Esters to α-Chloro Boronic Esters |year=1983 |last1=Matteson |first1=Donald S. |last2=Majumdar |first2=Debesh |journal=Organometallics |volume=2 |issue=11 |pages=1529–1535}}
:{{Chem2|H2CCl2 + RLi -> HCCl2Li + RH}}
Similar to n-butyllithium, tert-butyllithium can be used for lithium–halogen exchange reactions.{{cite journal |doi=10.15227/orgsyn.078.0051 |title=Synthesis of 4-, 5-, and 6-Methyl-2,2'-bipyridine by a Negishi Cross-Coupling Strategy: 5-Methyl-2,2'-bipyridine |journal=Organic Syntheses |year=2002 |volume=78 |page=51 |last1=Smith |first1=Adam P. |last2=Savage |first2=Scott A. |last3=Love |first3=J. Christopher |last4=Fraser |first4=Cassandra L. |doi-access=free |issn=2333-3553 }}{{cite journal |doi=10.15227/orgsyn.074.0248 |title=Regioselective Synthesis of 3-Substituted Indoles: 3-Ethylindole |journal=Organic Syntheses |year=1997 |volume=74 |page=248 |last1=Amat |first1=Mercedes |last2=Hadida |first2=Sabine |last3=Sathyanarayana |first3=Swargam |last4=Bosch |first4=Joan |doi-access=free |issn=2333-3553 }}
=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. 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.{{cite journal |author1=Stanetty, P |author2=Koller, H. |author3=Mihovilovic, M. |title=Directed ortho Lithiation of Phenylcarbamic acid 1,1-Dimethylethyl Ester (N-BOC-aniline). Revision and Improvements |journal=Journal of Organic Chemistry |year=1992 |volume=57 |pages=6833–6837 |doi=10.1021/jo00051a030 |issue=25}} In dimethoxyethane, the half-life is about 11 minutes at −70 °C{{cite journal |author1=Fitt, J. J. |author2=Gschwend, H. E. |title=Reaction of n-, sec-, and tert-butyllithium with dimethoxyethane (DME): a correction |journal=Journal of Organic Chemistry |year=1984 |volume=49 |pages=209–210 |doi=10.1021/jo00175a056}}
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.{{cite book |author=Errington, R. M. |title=Advanced practical inorganic and metalorganic chemistry |publisher=Blackie Academic & Professional |location=London |year=1997 |pages=47–48 |isbn=978-0-7514-0225-4 |url=https://books.google.com/books?id=yI_mq_mCf2AC&pg=PA47 |format=Google Books excerpt}} Serious laboratory accidents involving tert-butyllithium have occurred. For example, in 2008 a staff research assistant, Sheharbano Sangji, in the lab of Patrick Harran{{cite web |title=Harran Lab: UCLA |url=http://faculty.chemistry.ucla.edu/institution/personnel?personnel_id=552980 |access-date=2011-09-21 |archive-date=2012-10-13 |archive-url=https://web.archive.org/web/20121013013907/http://faculty.chemistry.ucla.edu/institution/personnel?personnel%5Fid=552980 |url-status=dead}} at the University of California, Los Angeles, died after being severely burned by a fire ignited by tert-butyllithium.{{cite news |publisher=Chemical & Engineering News |author=Jyllian Kemsley |title=Researcher Dies After Lab Fire |date=2009-01-22 |url=http://pubs.acs.org/cen/news/87/i04/8704news1.html}}{{cite news |publisher=Chemical & Engineering News |author=Jyllian Kemsley |title=Learning From UCLA: Details of the experiment that led to a researcher's death prompt evaluations of academic safety practices |date=2009-04-03 |url=http://pubs.acs.org/cen/science/87/8731sci1.html}}[http://www.latimes.com/news/local/traffic/la-me-uclaburn1-2009mar01,0,5638579.story Los Angeles Times, 2009-03-01]
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
References
{{Reflist}}
{{Lithium compounds}}
{{DEFAULTSORT:Butyllithium, t-}}
Category:Organolithium compounds