Chemical Forums

Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: mandy on March 21, 2007, 02:57:39 PM

Title: Grignard reagents lab
Post by: mandy on March 21, 2007, 02:57:39 PM

I'm doing a lab - preparing benzoic acid using a grignard reagent, and one thing i have to discuss in my introduction is the types of electrophile allowed, only i'm confused as to what the electrophile is (I know that an electrophile is a  reagent that is attracted to electrons and a nucleophile gives it's electrons to the electrophile, thus forming a bond).  To make a Grignard reagent from bromobenzene, the bromide takes the electrons from the bond that attaches it to the carbon, and then bonds to the magnesium, and then the magnesium bonds back on the carbon.  So i'm thinking that the Bromide is the electrophile, but i'm really confused,so if someone could explain whats going on i would appreciate it a lot, Thanks

Title: Re: Grignard reagents lab
Post by: alphahydroxy on March 21, 2007, 04:33:57 PM

I'm not exactly sure what you mean by "the types of electrohpile allowed", but I'd imagine the question is guiding you to think about the types of interactions of the grignard reagent after it is formed, rather than thinking about the mechanism of it's formation (which is much less conceptually clear cut).

You can think of the grignard reagent as "R-" (see the image below).

So, some things to consider are:

1.  Is the Grignard nucelophilic or electrophilic ?

2.  What does the answer to (1) imply that the grignard will react with?

3. What is the reactivity of the other reactant in the experiment?

Hope this helps...