Sunday, 23 January 2011

Lab Mishaps No. 1 - The Methyl Grignard Incident

As I sit here on a Sunday night pondering what tomorrow will bring for me in the lab, I can’t help but remember one fateful morning about a year ago. I was making a precursor to a range of catalysts I’ve been trying and working on about 20 g scale. It was a Kumada coupling reaction of an aryl triflate and a Grignard reagent:


Looks pretty innocuous, right? However, as any chemist worth his salt will know, MeMgBr is a sprightly little molecule and doesn’t much like air or moisture. All the glassware you use must be dried in an oven for a couple of hours before using it and the reaction must be carried out under an inert atmosphere (a balloon of argon in this case. A completely innocuous reaction, you might think. So I thought as well as a student three months into an MSc. I came in bleary-eyed at 9am on a Monday morning to see a red solution happily stirring away in its flask. I had left it a day longer than I normally would so I knew the reaction would be complete and all I had to do was a standard work-up to get my product. Adding Celite and removing any rubber bungs keeping air out followed by half hours stirring in air is the standard procedure.

But no, not this time. In my infinite wisdom, I decide to quench my reaction in a different way. “I’ll just add some water” I think to myself because that would quench the reaction far more quickly than the other method. So off I go to get a syringe and a needle. I push 2 mL of water into my reaction and all appears to be well. That is of course until the solvent (diethyl ether, which boils at 40 oC and has a horrible knack of setting on fire) starts boiling and my argon balloon starts increasing in size at what can only be described at an alarming rate. “Oh dear” I thought to myself as the balloon continued to expand. I decide the probable best course of action is to shut my fumehood sash and leave it to its own devices. As I do this, a rubber bung gives way and 300 mL of corrosive, caustic crap deposits itself on the glass in front of my face and across every other square centimetre of my spotless workspace along with a stripe of about a foot across my midriff.

Needless to say, the rest of the morning was spent wearing thick rubber gloves and wielding a squirty bottle of acetone and a roll of paper towel as I attempted to remove said crud from everywhere and the rest of the day was spent smelling slightly odd. I can only hope a repeat performance is not forthcoming in the future.

I’m contemplating making this a bit of a running feature of the blog as the majority of my workmates have done something equally stupid in their colourful times in the lab. It also seems a crying shame to keep them to myself, what do people think?

4 comments:

  1. Hahaha, oh man, that's a bit unfortunate. Gotta give your reaction enough time to get far enough along that exotherm. Good call closing the sash though! It could've been much worse.

    Lab accidents are always an interesting read. They definitely serve as a reminder, too, to keep your wits about you.

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  2. Hi!
    As a former Page group member (2004-2007), I actually did the same mistake as you did (with the Kumada coupling)! It's interesting to see my legacy continues!!
    Cheers
    Mohamed Farah

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  3. Ether actually boils at 34-35 C. Isn't lab live fascinating?

    mamid

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