re:ORGLIST: low temperature reactions

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From: A De (ocad$##$mahendra.iacs.res.in)
Date: Mon Oct 23 2006 - 01:54:59 EDT

Dear Mustapha/Puja,
Like Mustapha, we use mixture of liquid nitrogen and ethanol to attain
temperature of -70 degree and even below (-78degree) which we frequently
need for directed metalation reaction. A few words of caution however. As
ethanol continues to absorb water from atmosphere, which is particularly
true in hot and humid countries like India, efficiency of cooling rapidly
deteriorates. It is advisable to chasnge the ethanol bath after two
experiments and in the meantime to keep it in cupboard away from humidity.
Secondly the research students have the tendency to pour liquid nitrogen
in large cascades. It is impossible to maintain low temperature with
precision in this way. As one member of the orglist community has
observed, the whole bath freezes, the temperature is well beyond -70
degree and one of the annoyance is that the low temperature thermometer,
if you use one is ruined. With experience you can identify a certain
degree odf slushinees that tells you about the temperature. In my opinion
use of dry ice-acetone is a better way to attain low temperarure with
precision.
Asish

Professor Asish De
Project Investigator
Department of Spectroscopy
Formerly Professor Department of Organic Chemistry
Indian association for the Cultivaion of Science
Jadavpur; Kolkata - 700 032
India
Honorary Secretary,
Royal Society of Chemistry(Eastern India Section)
Tel : +91-33-2473-4971 (Ext : 271)
Fax : +91-33-2473-2805

On Fri, 20 Oct 2006, Mustapha Ouali wrote:

> Dear Pooja,
> I attained -70°C by mixing and stirring liquid nitrogen plus ethanol.
>
>
>
>> Dear all,
>>  Can anyone tell me the temperatures that can be attained by mixing liquid nitrogen with various solvents.
>>
>> Thanks
>> pooja
>>
>>
>
>
> Mustapha Ouali
> Universite Libre de Bruxelles
> Structure et Fonction des Membranes Biologiques (SFMB)
> Bd du Triomphe - C.P. 206/2
> 1050 Bruxelles
> Tel.+ 32-2-650.53.66
> Fax.+ 32-2-650.53.82
> E-mail: mouali$##$ulb.ac.be
>
>
>
>
>
>
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