Date: Tue, 6 Jan 2009 12:42:55 -0500
Reply-To: List Moderator <ecgrants**At_Symbol_Here**UVM.EDU>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: List Moderator <ecgrants**At_Symbol_Here**UVM.EDU>
Subject: Re: UCLA Lab Fire

From: 	info**At_Symbol_Here**
Subject: 	Re: [DCHAS-L] UCLA Lab Fire
Date: 	January 6, 2009 11:11:39 AM EST (CA)

I must clarify a few points and follow up on one or two.

1. The shorthand procedure Nameless Labmate used was deliberately  
brief, and relates the established procedure that was used in the  
laboratory.   It was not meant to be an instruction/endorsement, and I  
referred readers not only to Aldrich's web page which has the link to  
Bulletin AL-134 (Handling Air-Sensitive Reagents) but also  to my web  
page on pyrophoric materials that contains links to the their Bulletin  
AL-164 (Handling Pyrophoric Reagents).  I should have taken the time  
to explicitly point out that there are safer techniques, but in the  
interest of brevity on an already long post I did not make that clear,  
so thank you for taking the time to point that out.

2. There is no doubt that all BuLi reagents are dangerous and water- 
reactive, but t-BuLi will ignite even in dry air.  On an equimolar  
basis, t-BuLi *is* more dangerous; it is not only water-reactive, it  
is pyrophoric.   In my personal experience, I have never seen spilled  
n-BuLi in the 1 to 2.5 M range spontaneously ignite in ambient air,  
but it obviously could if, for example, it landed near, for example,  
water on a condenser etc. or one was using some unusually high  
concentration.   And to be clear, the n-BuLi I spilled on my hand was  
1-2 M (as we always titrated our bottles before use).  My hands are a  
source of moisture, and while the reagent clearly reacted with my  
fingers, they did not catch fire, but it they did get warm from the  
heat of the reaction!   That said, Joseph is correct in that all of  
these substances need to be treated with great respect, and nobody  
should infer that n-BuLi is somehow "safe" or won't catch fire.

3. Sure Seal bottles are a fine device and I encourage the proper use  
of those bottles.  I should have explicitly added to the Lessons that  
you have to maintain them; I alluded to that with the Parafilm comment  
but didn't finish up.  I have seen nBuLi and Grignard Sure-Seals with  
gaping holes in them.  If your bottle reaches that kind of state, the  
best thing to do is a cannula transfer into a new empty Sure Seal  
bottle or other suitable storage container.  Parafilming and "getting  
by" with jury-rigged solutions contributes to accidents, a point I  
hope was clear from the original post.

4. A good chemist will *always* titrate their alkyllithium and related  
compounds before use.  These are easily done on a very small scale and  
take just a few minutes.  As Joseph notes below, akyllithiums are  
notoriously unstable, and the concentration in the bottle can be  
significantly higher (from solvent evaporation or precipitation, for  
example) or lower (from air/water infiltration) than the what is given  
on the label.   Titration is even more important for Grignards which  
tend to come in ethers and undergo Schlenk equilibria to mixtures of  
RMgX, MgX2 and R2Mg.  Never rely on what the bottle says for  
concentration, even for a "fresh" bottle.  And, most importantly, use  
the correct titration method for your reagents.  Some methods do not  
give good results for certain reagents, so do a careful literature  
search to determine the best method.


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