From: "Pickel, Joseph M."
Date: January 6, 2009 9:36:20 AM EST (CA) Subject: RE: [DCHAS-L] UCLA Lab Fire Folks- For what its worth, having worked in the lab for almost 10 years with n-BuLi, sec-BuLi, and t-BuLi, and a variety of their derivatives, I am dismayed by some of the advice given in the previous message. The incorporation of opinions and speculation takes away from the fact that alkyl lithiums are truly hazardous materials and whether or not the author agrees with the facts of the newspaper article, it seems that in one way or another, some poor student has sustained serious burns by coming into contact with an alkyl lithium compound. That being said--- these materials can be handled safely (even in sure-seal bottles) by personnel who understand the hazards of the material and take the appropriate precautions. I will not go into great detail about what precautions must be taken to handle alkyl lithiums and other pyrophoric materials, but I do want to dispel some of the generalizations proposed in the previous note - ***The pyrophoricity of alkyl lithiums will depend on concentration, solvent, humidity etc... generalizations ala t-BuLi will be more pyrophoric than n-BuLi are not necessarily accurate or helpful and no one should be given the idea that a t-BuLi is significantly more dangerous than others! Alkyl lithiums come in a variety of solvents at a variety of concentrations and almost every one of these solutions will catch fire if exposed to a suitably humid atmosphere. That being said, the author of the previous letter was probably working with a very old and therefore less concentrated bottle of n-butyl lithium when he got it on his hand which is why it didn't burn. - Sure-seal bottles aren't perfect, but they provide a safe way to handle alkyl lithium solutions in a bench top environment. Unless the seal is punctured by a very large gauge syringe or a nail, the seal is sufficient to prevent moisture from entering the bottle and causing big problems. - The technique described below for withdrawing/dispensing solutions from a sure-seal bottle is the lazy/ quick and dirty way of doing things and can lead to significant hazards- I would not recommend them to anybody. Better methods are described in the Aldrich technical bulletin cited here-http://www.sigmaaldrich.com/etc/medialib/docs/Aldrich/Bulletin/al_techbull_al134.Par.0001.File.tmp/al_techbull_al134.pdf - I agree that purchasing large containers of chemicals for purposes of cost savings is a bad idea, but that statement ignores the problem of how to tell an ordinary chemist with a limited budget about the merits of small containers. However, purchasing alkyl-lithium compounds in small bottle is a no-brainer even for the thrifty chemist! You see- even in the best storage conditions (complete sealed from the atmosphere under an inert gas blanket and in the Fridge) alkyl lithium compounds degrade over time to more stable components. Therefore, the concentration of the alkyl lithium solution marked on the label is almost always higher than what is actually in the bottle. That means for a given reaction- the chemist must either determine the concentration of the solution prior to each use or use an increasingly large excess of solution for each experiment... either one of the workaround techniques is less cost- efficient that buying a small bottle on an as needed basis. Be safe, Joseph M. Pickel, Ph.D., CCHO
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