[estupidoquimico]

I still don't quite understand the main difference between Grignard and Barbier reactions based on their definitions. Is it the metal used? Substrate? Mechanism?

Suppose I want to make an alpha-benzyl alcohol from benzaldehyde and an alkyl bromide. If I use magnesium. Would that automatically make it a Grignard reaction instead of Barbier?
And how come Barbier reaction is less sensitive to water?

Thank you so much in advance

[Hunter2]

The reactions are similar

But

The reaction is similar to the Grignard reaction but the crucial difference is that the organometallic species in the Barbier reaction is generated in situ, whereas a Grignard reagent is prepared separately before addition of the carbonyl compound.

From wiki

[Vidya]

https://en.wikipedia.org/wiki/Barbier_reaction
This link is clearly explaining the difference.

[estupidoquimico]

Thank you very much for your answers.

But sorry, I still do not understand. Because on the Wikipedia page, it says that the difference is the organometallic species is generated in situ. So, is it just a matter of substrate addition then?

In the case of making an alpha-benzyl alcohol from benzaldehyde and an alkyl bromide using magnesium.
If I add the alkyl bromide to the magnesium, and wait until the organomagnesium is formed before adding benzaldehyde. That is a Grignard reaction, right?
But, if I add them simultaneously, would that make it a Barbier reaction?

Wouldn't in both cases the organometallic compound, hence the mechanism, be the same?

Then how come one is less sensitive to water than the other?

[Vidya]

Mg is very reactive metal as compare to Zn or Sn.In barbier reaction we are using Metals or metal compounds.Like there is one book Organic chemistry by Louden and in this Barbier reaction is with Zn or Sn or less reactive metals.So it can be that in Barbier reaction a Magnesium compound is used and not pure Magnesium metal to make it less susceptible to water.

[rolnor]

Its very, very clear, exactly what the difference is if you read the Wiki.
https://en.wikipedia.org/wiki/Barbier_reaction