Grignard Reagent: When does it act as Nuc vs Base ?

[RangeRover89]

I have found no explanation for when it acts as a base vs a nucleophile in my book?

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[discensdentibus]

I can't see the image? This may just be me, but a grignard is gonna be a base when there are hydrogens to pluck off. EX: water, alcohol, thiol, RCOOH, phenols, amines (except quaternary). Grignards need dry conditions, and your book might go into the solvents used. Usually bat ether or THF is used. This may sound lame, but it is going to act as a nucleophile in the presence of an electrophile. There are many electrophilic sites of attack. ex: nitriles an carbonyl compounds

 

[RangeRover89]

yeah, thank you. what about when it is with a water as a solvent after? i am guessing that the nuc only happens if its an aldehyde or ketone...

 

[discensdentibus]

grignards get destroyed in water. if its a humid day, you literally can't do grignard in labs because it messes them up. You have to take into account why though for this to stick. Think about electronegativity different and pka

 

[Daneosaurus]

Gringards are extremely basic, which is why the acid work up step is required after the reaction.

They always act as a nucleophile.

 

[biomolecmed]

If you have like carbonyl or a nitrile, then grignard is a nucleophile. However, if you have an acidic proton, such as water, or alcohol, Grignard acts like a base and picks up that proton. Hope this helps.

 

[futuredoc331]

Use Orgo as a Second Language by Klein. Absolutely the best book out there. Two easy A's thanks to the first and second semester books.