For Orglist : Carboxyaltion problem

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From: Vijay Sane (vsane$##$hotmail.com)
Date: Thu Jun 21 2001 - 09:34:24 EDT



Recently I was carrying out carboxylation of dichloro phenols potassium salt
in xylene, under CO2 pressure 20 kg/cm2. at 140 degrees centigrade, by usual
Kolbe-Schmidt's method.
During isolation of the dichloro salicylic acid dipotassium salts by
filteration at 120 degrees centigrade ( which is preferred so as to separate
unreacted dichloro phenol ), wash by xylene solvent, all under CO2 pressure
of about 1-2 kg/cm2; suddenly the pressure went up, opening up the safety
valve, and there was fire. The entire cake burned out leaving only
carbonised residue.
The xylene just got carried out of the pressure filter, when the safety
valve opened up, indicating it did not get burned probably because there was
no oxygen present in the filter.
I tried to look in literature, but so far no reports have been made of any
of such incidents.Can anyone help me out, why this thing happened at all?
Again so far I have carried out 12 experiments without any problems,
all the raw materials are from same source, so what might have gone out of
control?
Regards
Vijay Sane
vsane$##$hotmail.com
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