Green Chemistry @ MUN


Fieser and Fieser: A Labful of Tips
November 25, 2013, 12:52 pm
Filed under: Uncategorized

Useful potassium tert-butoxide purification method and a reminder of an old trick for preparing your Grignard reagents 🙂

Chemtips

It’s hard to look back and not wonder what we’ve lost.  Organic chemistry is not immune to fickle trends and fashion, and more than one darling of yesteryear lies forgotten in the dusty pages of Tet. Lett. [1].  While I’ve no desire to go back to preparing platonic solids, there’s a few tricks I feel happier to have up my sleeves.

1) Ethylene dibromide/1,2-Dibromoethane is a Grignard Entrainer/Initiator

Grignard reactions are notoriously finicky, which is why they are a standard feature in second-year organic chemistry labs.  The key lies in initiating the reactions.  Exposure to oxygen leaves a thin film of magnesium oxide on the surface of the metal, which weak bromides are unable to pierce.

Ethylene bromide is far stronger than your average electrophile, and will rapidly clear the magnesium oxide.  The product is ethylene gas, allowing both a clear sign that the grignard is proceeding and…

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