SixTough
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Grignard intermediate halogenation (or substitution)
Hello dear Sciencemadmen, I have a question.
I usually utfse and find whatever i'm interested in but this time i am not even sure how to name what i'm looking for.
When a Grignard reagent is combined with CO2 it forms an intermediate described as
RMgX + CO2 = RCOOMgX.
Hydrolyzed it gives a carboxylic acid.
Has anybody hard of a reaction producing an acid halide, like
RCOOMgX + X2 = RCOOX + MgX2 ?
Im not very good at nucleophillic substitutions by the way.
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Nicodem
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Magnesium salts are of no preparative use for that reaction as the equilibrium is leaned toward the left side. You need a silver(I) carboxylate which
gives the RCOOX irreversibly, driven by the covalent nature of AgX and their insolubility. Hg(II) carboxylates also work to some extent due to the
covalent nature of HgX2 compounds. The so formed RCOOX intermediates are unstable, can't be isolated as far as I know, and decompose to RX and CO2.
See the Hunsdiecker reaction mechanism.
PS: RCOOX compounds are not acid halides (or acyl halides). Carboxylic acid halides are RCOX.
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SixTough
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Yup, heard of that one.
Sorry Nicodem got a little confused there, happens when you post late at night.
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