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I have heard of the leveling effect, which mentions that highly basic ions cannot exist in a solvent if it's acidity is high enough to be deprotonated by the base.

Considering that, check out the Grignard reagent. I'll use a methylgrignard for this purpose, generated in a diethylether solvent.

This Grignard reagent furnished methanide ions ($\ce{CH3-}$). This ion can abstract protons from any compound thats more acidic than methane. Diethyl ether possesses $\beta$-hydrogens that are easily abstracted due to the inductive pull of the oxygen atom:

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The inductive pull may not be much, but it certainly makes it more acidic than a regular hydrocarbon hydrogen.

However we know that Grig reagents do work in ethereal solvents. How is it so?

Edit: This isn't a duplicate of the mentioned question. My question deals with acidity of $\beta$ hydrogens.


marked as duplicate by ringo, paracetamol, Nilay Ghosh, airhuff, Mithoron Jun 22 '17 at 15:13

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • $\begingroup$ True, the question asks something different. The answer will be largely the same. Voting to leave open (as per site policies) and waiting for someone to give practically the same answer, referencing the other question ;) $\endgroup$ – Jan Jun 22 '17 at 11:48

We tend to assume that acid-base reactions are instantaneous. But they need to go through an activated complex of higher energy, like every other reaction.

These reactions are usually done at - 78°C. As long as the energy provided to the system is below that which is required to reach the activated complex there should be no reaction.

I know for sure that tetrahydrofuran is fully deprononated by nBuLi at room temperature. The color turns deep yellow, if I recall correctly.

  • $\begingroup$ Um, is thf a typo for "the" and what is nBuli? $\endgroup$ – Pritt Balagopal Jun 22 '17 at 3:08
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    $\begingroup$ I think they mean "tetrahydrofuran by normal butyl lithium" $\endgroup$ – Bob Jun 22 '17 at 3:50
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    $\begingroup$ @user46680 Do you have any sources to support your assertion? For example, which sources did you get the part about the thermodynamics of acid-base reactions (i.e. "they need to go through an activated complex of higher energy")? Just want to ascertain the accuracy of your answer. $\endgroup$ – Tan Yong Boon Jun 22 '17 at 5:47
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    $\begingroup$ @Tan The concept of activated complex and energy of activation is broadly covered by most books of statistical thermodynamics. This one is a good one "Statistical Thermodynamics M. C. Gupta" $\endgroup$ – user46680 Jun 22 '17 at 10:43
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    $\begingroup$ THF is tetrahydrofurane, nBuLi is butyl lithium, the n says that the carbon chain is linear $\endgroup$ – user46680 Jun 22 '17 at 10:45

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