Comments on: Formation of Grignard and Organolithium Reagents

By: Oliver

Oliver — Wed, 09 Mar 2022 01:59:12 +0000

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By: James Ashenhurst

James Ashenhurst — Fri, 22 Oct 2021 18:18:19 +0000

Should be a carbanion. Is there a typo somewhere I’m not seeing?

By: Mike

Mike — Tue, 29 Sep 2020 08:05:32 +0000

The grignard reagent (say Ch3mgbr) can act as a base here thereby abstracting the acidic hydrogen from terminal triple bond carbon. But still we get a carbocation!!

By: James Ashenhurst

James Ashenhurst — Fri, 25 Sep 2020 16:02:00 +0000

In reply to Mike.

First, draw out (or at least imagine) the Grignard that would form from 3-bromoprop-1-yne.
Next, think about how basic this species is. Remember the pKa’s of alkanes are around 50 (this one would be slightly less, but still).

Are there any acidic protons around that could react with this very basic Grignard reagent?

By: Mike

Mike — Wed, 23 Sep 2020 08:04:17 +0000

Why can’t 3-bromoprop-1-yne form grignard reagent?

By: James Ashenhurst

James Ashenhurst — Wed, 15 May 2019 02:24:58 +0000

In reply to Farwa.

From my friend Jeff, who regularly used Li metal to make lithium di-tertbutyl diphenylide (LDBB).
Lithium prep:
tweezers
1 pair of needle-nose pliers
Lithium wire (usually with a small % of Na in it) in oil
3 beakers: hexane, THF, and MeOH, and then a 4th with reaction solvent (or just the reaction itself, with an ARGON atmosphere, preferably)
Cut wire into pieces with scissors or pliers and put into hexanes
Use tweezers to fish out a piece of Li and squish with pliers and return to hexanes
Once all the pieces have been pressed, use tweezers and take a piece out of hexanes and dip in THF then MeOH then THF again and then into the reaction solvent/flask.
Repeat with remaining pieces of Li

By: James Ashenhurst

James Ashenhurst — Thu, 21 Mar 2019 15:10:24 +0000

In reply to Sufia. Yes, LiBr dissociates, although you'd have to look up the solubility in water to get a precise number.

By: Yujie

Yujie — Tue, 13 Mar 2018 13:19:03 +0000

In reply to James. Yeah, we need Grignard reagents because lithium introduces impurity to our system

By: James

James — Mon, 12 Mar 2018 21:41:14 +0000

In reply to Yujie. Do they need to be Grignards? Or can they be organolithium reagents?

By: Yujie

Yujie — Mon, 12 Mar 2018 17:05:36 +0000

Thanks for sharing!
So because of Schlenk equilibrium, Et2O or THF is necessary for the synthesis of Grignard reagents, right? My research project now requires Grignard reagents, but THF or Et2O is not good for the whole reaction system, I’m trying to synthesize Grignard reagents in some non-polar solvents such as toluene, I’m wondering if it’s possible?