N-Butyllithium

Abstract

[109-72-8] C4H9Li (MW 64.05) (strong base capable of lithiating carbon acids;1 useful for heteroatom-facilitated lithiations;2, 3 useful for lithium–halogen exchange;1, 4 reagent of choice for lithium–metal transmetalation reactions1a,c,5) Physical Data: colorless liquid; stable at rt; eliminates LiH on heating; d25 0.765; mp −76 °C; bp 80–90 °C/0.0001 mmHg; dipole moment 0.97 D.6 13C NMR, 1H NMR, 6Li NMR8 and MS studies have been reported.7-9 Solubility: sol hydrocarbon and ethereal solvents, but should be used at low temperature in the latter solvent type: half-lives in diethyl ether and THF have been reported;10 reacts violently with H2O and other protic solvents. Form Supplied in: commercially available as approximately 1.6 M, 2.5 M, and 10.0 M solution in hexanes and in cyclohexane, approximately 2.0 M solution in pentane, and approximately 1.7 M, and 2.7 M solution in n-heptane. Hexameric in hydrocarbons;1c tetrameric in diethyl ether;1c dimer–tetramer equilibrium mixture in THF;11 when used in combination with tertiary polyamines such as TMEDA and DABCO, reactivity is usually increased.1, 12 Analysis of Reagent Purity: since the concentration of commercial solutions may vary appreciably it is necessary to standardize solutions of the reagent prior to use. A recommended method for routine analyses involves titration of the reagent with s-butyl alcohol using 1,10-phenanthroline or 2,2′-biquinoline as indicator.15 Several other methods have been described.16 Preparative Methods: may be prepared in high yield from n-butyl chloride13 or n-butyl bromide14 and Lithium metal in ether or hydrocarbon solvents. Handling, Storage, and Precautions: solutions of the reagent are pyrophoric and the reagent may catch fire if exposed to air or moisture. Handling of the reagent should be done behind a shield in a chemical fume hood. Safety goggles, chemical resistant gloves, and other protective clothing should be worn. In case of fire, a dry-powder extinguisher should be used: in no case should an extinguisher containing water or halogenated hydrocarbons be used to fight an alkyllithium fire. Bottles and reaction flasks containing the reagent should be flushed with N2 or preferably Ar and kept tightly sealed to preclude contact with oxygen or moisture. Standard syringe/cannula techniques for air and moisture sensitive chemicals should be applied when transferring the reagent. For detailed handling techniques see Wakefield.1b