Methyllithium

Abstract

[917-54-4] CH3Li (MW 21.98) (methylating agent for several functional groups; cleaves protecting groups; synthesis of other methyl organometallics, i.e. of Cu, Ga, Ti, Mg, Si, Ir, B; can function as a base; reduces transition metals) Physical Data: unsolvated solid is pyrophoric; densities listed below. Solubility: insol hydrocarbon solvents; moderately sol ethereal solvents; reacts exothermically with water and protic solvents to generate methane. Form Supplied in: commonly available as >1.4 M in diethyl ether, d >0.732 g mL−1; >1.5 M in diethyl ether (with ≈1.0 equiv of LiBr), d >0.852 g mL−1. New formulations are >1 M in THF/cumene with 0.08 M Me2Mg,1 d 0.86 g mL−1; 70 wt % solid2 complexed with 22 wt % diethyl ether, 6% LiCl, and ≈1% LiOH. Analysis of Reagent Purity: titration of 0.5 N s-butanol in toluene (10 mL) with methyllithium via tared syringe at 15 °C using 2,2′-biquinoline as an indicator. Handling, Storage, and Precautions: methyllithium in diethyl ether is pyrophoric in absence of LiBr, according to US Dept of Transportation regulations (49 CFR 173, Appendix E), while all other available formulations (solution and solid) are nonpyrophoric. Store in a cool, dry place in a tightly sealed container under an inert atmosphere.