MgBr+ -- Where is the charge at? What is the name of it?

[Genecks]

I'm looking over synthesizing alcohols with grignard reagents.

 

I'm going batty trying to figure out where the positive charge is on MgBr+.

Is it on the Br? The Mg? Is it localized all over, as in [H3O]+? Thus being [MgBr]+?

 

Also, what is the name of the MgBr+?

 

ChemSketch didn't seem to help in this department.

Edited February 7, 2011 by Genecks

[hypervalent_iodine]

The positive charge would lie on the magnesium. MgBr⁺ is simply a magnesium bromide ion. This species doesn't have much of anything to do with the actual Grignard reaction though. At the end of a Grignard reaction you get Mg(OH)Br, which then goes on to react with the acid you'd have in solution to form water, bromide ions and Mg²⁺.

Have a read of this, it might help.

 

 

Edited February 7, 2011 by hypervalent_iodine

[mississippichem]

Though the ion only exists fleeting in a Grignard solution, its formal name is bromomagnesium(II).

[Horza2002]

The positive will be on the magnesium as it is more electropositve than bromine (or bromine is more electronegative depending on how you want to look at it).

[TheLivingMartyr]

all wrong sorry, didnt look properly

Edited February 12, 2011 by TheLivingMartyr

[hypervalent_iodine]

all wrong sorry, didnt look properly

 

 

...what?

 

 

[StringJunky]

...what?

 

He/she made a post and realised it was wrong /irrelevant resulting in its deletion...they didn't mean any of you were wrong...I interpreted it that way at first then saw the editing note

[hypervalent_iodine]

He/she made a post and realised it was wrong /irrelevant resulting in its deletion...they didn't mean any of you were wrong...I interpreted it that way at first then saw the editing note

 

 

Ah, gotcha. Didn't look at the edit button.

 

 

[adianadiadi]

I think MgBr⁺ might be written in the equation showing Grignard reaction.

 

This species represents Mg²⁺ and Br^-. But these ions exist in the aqueous solution separately.

[mississippichem]

I think MgBr⁺ might be written in the equation showing Grignard reaction.

 

This species represents Mg²⁺ and Br^-. But these ions exist in the aqueous solution separately.

 

A Grignard reagent exists in what's called the Schlenck Equilibrim. The alkyl magnesium bromide is in equilibrium with a dihalomagnesium and dialkylmagnesium species. It has been postulated but not confirmed that a halomagnesium cluster is involved as well.

Edited February 13, 2011 by mississippichem