Grignard Reagent

[dttom]

This reagent is able to convert aryl halide to Ar-MgX through formation of free radical of Ar., but I wonder why this could be done, as there should be resonance over seven atoms, but it becomes over six atoms after the reaction.

I am not sure if the 3p orbital of Mg could participate in resonance.

 

I also wonder if the Grignard reagent could be used for the same purpose with phenol or aniline, or those which more significant delocalization of pi electrons.

 

Thanks very much.

[hermanntrude]

when a reaction occurs, the new product isn't always more stable than the reactants.

[John Cuthber]

when a reaction occurs, the new product isn't always more stable than the reactants.

 

Generally, at least one of the products is more stable. Things like organometalic reagents can do neat tricks because one of the products is something very stable like salt or MgCl2.

 

A grignard reagent with phenol will just deprotonate it to give magnesium phemoxide and an alkane.

I'm not sure but I think much the same will happen with aniline.

[dttom]

I see the logic between Grignard reagent and phenol or aniline now.

But what about that between Mg metal and phenol or aniline, would phenol be converted to Ar-MgOH, it seems a bit ugly though the aromaticity is still there if considering Ar-...

[adianadiadi]

Grignard reagent is formed from an organic halide and magnesium in ether solvents. But they are highly basic and hence can react with protic compounds like aniline or phenol. Hence they wont give grignard reagents.

 

Read more information about this at Grignard Reagent by AdiChemAdi

Edited September 5, 2010 by adianadiadi

[mississippichem]

Grignard reagent is formed from an organic halide and magnesium in ether solvents. But they are highly basic and hence can react with protic compounds like aniline or phenol. Hence they wont give grignard reagents.

 

Yeah, a Grignard reagent is essentially a masked carbanion stabilized by the highly argued Shleck equilibrium. The pKa for a carbanion is huge. People even have trouble studying them because they're half-lives are often times shorter than [math] sp^2 [/math] carbocations. Some Grignards are so basic they will rip off alkenyl or even vinyllic hydrogens in some substrates.

Edited September 5, 2010 by mississippichem