Does methyl lithium act as a base in aqueous solution?

1 Answer
anor277
Oct 28, 2015

Well, you're right, but #CH_3^-# as a species is highly reactive.

Explanation:

Any solvent system moderates (or magnifies) the strength of the acids or bases it solvates. In water, the strongest base is #OH^-#. Addition of non-aqueous bases such as methyl lithium would increase concentration of hydroxide according to the following equilibrium:

#CH_3Li + H_2O rarr CH_4(g) + LiOH(aq)#

Such a reaction would be rapid and very exothermic AND QUANTITATIVE...the solution would be stoichiometric in lithium hydroxide. Most of the time, when we store and use lithium reagents, we go to elaborate lengths (i.e. inert atmospheres, flame dried glassware, anhydrous solvent) in order to prevent such reactions.

I could conceive that we could take an anion (methyl lithium itself, or THE ANION formed by reaction with methyl lithium), and treat this with heavy water, i.e. #""^(2)H_2O#, and thereby introduce a deuterium isotopic label in the parent molecule, i.e. to give #H_3C^2H#...

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