Date: Fri, 10 Mar 2006 11:42:21 -0800
Reply-To: "Latimer, Lee" <lee.latimer**At_Symbol_Here**ELAN.COM>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: "Latimer, Lee" <lee.latimer**At_Symbol_Here**ELAN.COM>
Subject: Re: Questions out of my realm
Comments: To: "DanielD734**At_Symbol_Here**AOL.COM"

Daniel's suggestion of the CO2 is good.  

I presume that the reason to quench to butyl lithium solution is that it is
a residue in a large bottle.  Thus small amounts.  Many businesses now do a
lab pack for disposal rather than quench.

Quenching into alcohols, ethanol or IPA, is fine as long as it is under a
positive pressure of N2 and transferred by syringe.  The N2 should be
attached through condenser to a flowing system which will serve to carry the
butane away from the reaction location and can be directed into the hood
vent.  It is a good idea to dilute the alcohol with an inert solvent to slow
the quench a bit.  The use of syringe or dropping addition funnels is
control of the rate, which is less likely in my opinion with pressurized
transfers.  As always with safety, it takes a bit longer to do it safely,
but the rewards are great.

A less well used version is to add to a solution of ethyl acetate, as in the
case of CO2, to minimize outgassing.

In either case, always add the reagent to be quenched to the excess
quenching solution by a manner that allows control of addition and resulting
heat generation.

I had the unfortunate privilege of writing up a report and recommendations
on how to do this years ago when an entire lab went up as a result bad
technique and resulting panic in quenching nBuLi residues.

Of course, also refer to the MSDS and to the Encyclopedia of Reagents for
Organic Synthesis.

As for the ether issue in the original email, distillation apparatus under a
N2 atmosphere is best (see butane comment above).  Many of us have
concentrated ether under boil off conditions.  I find it best to conduct the
vapors away to the hood vent.  Sounds like someone turned up the hot plate
pretty hot, or the hood wasn't effective.  Other solvents are also useful
since the low boiling point of ether gives little latitude for using
solubility improvements at higher temperatures.


-----Original Message-----
From: DCHAS-L Discussion List [mailto:DCHAS-L**At_Symbol_Here**LIST.UVM.EDU]On Behalf Of
Sent: Friday, March 10, 2006 11:08 AM
To: DCHAS-L**At_Symbol_Here**LIST.UVM.EDU
Subject: Re: [DCHAS-L] Questions out of my realm

A safer butyl lithium quench:
Slowly add the butyl lithium ( using a double tipped needle with nitrogen  
pressure) to crushed dry ice. The butyl group adds to CO2 and forms the
salt of pentanoic acid. The dry ice also keeps everything very cold.
When adding butyl lithium to alcohol, butane is formed along with lots of  
heat. You are setting yourself up for a  fire/explosion.

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