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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Molossus on February 10, 2008, 11:26:40 PM

Title: Side Products Grignard Reagant
Post by: Molossus on February 10, 2008, 11:26:40 PM

Anyone know any possible side products you could get from reacting 1) Bromobenzene and Magnesium to form phenylmagnesium bromide and 2) phenylmagnesium bromide and methyl benzoate to form triphenylmethanol . I can't think of any

Title: Re: Side Products Grignard Reagant
Post by: macman104 on February 11, 2008, 04:42:24 AM

I can't see any either, the only thing would be a possible steric factor, but CCl₄ can go to triphenylchloride, so I don't think it will be an issue.

Title: Re: Side Products Grignard Reagant
Post by: AWK on February 11, 2008, 06:33:20 AM

What about reaction of Grignard reagent with traces of water or carbon dioxide from air?

Title: Re: Side Products Grignard Reagant
Post by: Sev on February 11, 2008, 06:42:30 AM

Biphenyl

see: http://www.mnstate.edu/jasperse/Chem355/Grignard.doc.pdf

Title: Re: Side Products Grignard Reagant
Post by: macman104 on February 11, 2008, 01:18:31 PM

Quote from: AWK on February 11, 2008, 06:33:20 AM

What about reaction of Grignard reagent with traces of water or carbon dioxide from air?

I didn't really count those, as those are sort of possible in any grignard reaction, I was thinking of things specific to the reaction itself.  But yea, biphenyl is a possible byproduct.

Title: Re: Side Products Grignard Reagant
Post by: jamaal on February 11, 2008, 01:33:54 PM

Hmm..I don't understand how'd you get triphenylmenthanol when you are only reacting two molecules with benzene rings.  As for side products you'd probably get some other derivatives of the alcohol because reactions usuall do not have a 100% yield.  There will also be some sort of organometallic product from the use of the Grignard reagent.

Title: Re: Side Products Grignard Reagant
Post by: sjb on February 11, 2008, 02:36:21 PM

Quote from: jamaal on February 11, 2008, 01:33:54 PM

Hmm..I don't understand how'd you get triphenylmenthanol when you are only reacting two molecules with benzene rings.

Consider what happens when you react a generic ester with a generic Grignard...

S

Title: Re: Side Products Grignard Reagant
Post by: Sev on February 11, 2008, 05:46:56 PM

See mechanism I posted yesterday.

Title: Re: Side Products Grignard Reagant
Post by: azmanam on February 12, 2008, 08:57:06 AM

You may also see another "byproduct" experimentally if you don't have a supersoichiometric amount of your nucleophile.