Re: ORGLIST:Details of Kipps-like generation of CO2?

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From: David O'Dell (dko$##$ou.edu)
Date: Mon Aug 26 2002 - 12:24:03 EDT


Dr. Lalor,

A good way to carboxylate grignard reagents is to pour the preformed
Grignard over crushed dry ice (solid CO2).

Hope this helps.

David O'Dell
University of Oklahoma

At 10:55 AM 8/26/02 +0300, Jacob Zabicky wrote:
>Hello Fergus,
>
>Two alternatives for which you have to decide the actual size of parts you
>need.
>
>1. IMHO the simplest. You need a glass stopcock or a needle valve or any
>flow regulating device, with one outlet long enough to dip into the
>solution, the other one wide enough to stick into the opening of a rubber
>baloon (you may need to reinforce that with a rubber band or a bracket so
>the baloon doesn't fly away) . Open the valve, inflate the baloon with CO2
>from a cylinder to a reasonable size, close the valve and stick the long
>end in your reactor. Voila! Keep a few baloons handy for replacement.
>
>2. I'm looking into a "Fisher" catalog, any other catalog may be fine. The
>only thing that is important is the shape of the parts. You decide on the
>size. In the Distillation section youl find "Pyrex brand vacuum type
>distillation traps," you'll need two of these, not necessarily of the same
>size (they will be parts A and B). In the Funnels section you'll find
>"Cylindrical separatory funnels," you'll need one of these (part C).
>Connect the side tube of part A (the bigger one) to the vertical tube of
>part B. Put some glass wool (rather loosely) in the side tube of part B and
>connect that to a tube dipping into the solution. stick the stem of part C
>into the vertical tube of part A and seal the space between the tubes.
>Place some dilute H2SO4 in the vessel of part A and some concentrated H2SO4
>in the vessel of part B (the vertical tube of part B should dip into the
>acid). Close the stopcock of part C and place some Na2CO2 solution in the
>cylinder. Carefully open the stopcock of part C and start generating moist
>CO2. The moisture will be absorbed in part B. The glass wool serves to
>knock out any droplets of acid that will interfere with the Grignard
>synthesis. You may sort out the details of concentrations a dripping rate
>of carbonate solution.
>
>Have fun,
>
>Jacob
>
>At 18:35 21/8/2, F.J. Lalor wrote:
> >Ok - I am fully aware that this is a shamefully elementary question
> >so no finger-wagging from the intellectual elite please 8-)
> >For the purposes of a u/g lab experiment I need to generate small
> >quantities of CO2 - preferably from a Kipps apparatus or something
> >similar - to do a small-scale carbonation of PhMgBr. (Of course a
> >cylinder would be easier but .... well, there are reasons). Now of
> >course I know that all I need to do is drop sulphuric acid on calcium
> >carbonate. Problem is I cannot find specific details anywhere. All
> >the older practical textbooks in our library that might have
> >described the experiment have long ago been dumped. So do I need
> >conc. or dilute sulphuric acid? How do I dry the CO2 and avoid
> >entrainment of acidic vapours? Any and all advice will be most
> >gratefully appreciated.
> >Regards -
> >Fergus Lalor
> >--
> >
> >--------------------------------------------------
> >Dr. Fergus Lalor, Senior Lecturer, Chemistry Dept., University
> >College, Cork, IRELAND.
> >Telephone: 353-(0)21-4902317. Fax: 353-(0)21-4274097
> >
> >
> >
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>Prof. Jacob Zabicky
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