From: Jacob Zabicky (zabicky$##$bgumail.bgu.ac.il)
Date: Sun Aug 11 2002 - 01:51:10 EDT
Hello again,
If we come to microwave reactors, as Darren suggested, ultrasound is also
a possibility. IMO in both cases you will need a specially designed vessel,
both to allow inflow of energy to the reaction mixture and to avoid outflow
if the deletereous bromine vapors.
All the best,
Jacob
At 13:15 8/8/2, Darren Rhodes wrote:
>It would be interesting to this sort of thing under microwave conditions ...
>This should bring down your reaction time and if you wanted to do the work
>on a larger scale you could use a continuous flow microwave reactor ... For
>the batch microwave work talk to http://www.personalchemistry.com/ (the web
>page seems a bit bloated but it should give you contact details). For the
>continuous flow ... maybe the personalchemistry people again ??? Perhaps
>someone else on the list could give appropriate details and refs and perhaps
>their own experiences of these techniques .....
>
>Darren.
>
>----- Original Message -----
>From: "Jacob Zabicky" <zabicky$##$bgumail.bgu.ac.il>
>To: <suzukicar$##$belais.freesurf.fr>; <everybody$##$orglist.net>
>Sent: Thursday, August 08, 2002 12:32 PM
>Subject: Re: ORGLIST:Bromination
>
>
>Hello Bel,
>
>The pressure in the vessel will be somewhat lower than 4 bar. If your
>reaction mixture is over a couple of mL, you should carry out the process
>in a Teflon-lined pressure vessel. If you can do it in small batches,
>then you can prepare thick-walled test tubes, of outer diameter not bigger
>than say 10 mm, place your mixture, freeze it with ice-salt or other
>cooling medium (below -10C), and seal the tubes while slightly evacuating
>at the end.
>
>You can place the tubes in boiling water or in a temperature-controlled
>heating block, all this, of course in a well protected hood. Thick-walled
>tubes of small diameter withold some pressure quite well.
>
>Good luck,
>
>Jacob
>
>
>At 16:23 7/8/2, Bel wrote:
>>Dear all,
>>
>>I would like to know If any has experience with bromination in harsh
>>conditions, using sealed tube at high temperature. I found one procedure
>>concerning the bromination of an electronically poor aromatic (pyridinium
>>derivative) which must be done by heating during 3 days at 180C. The
>>bromine's boiling point is 58.7C, which means a very high pressure in the
>>tube at 180C. So does anyone know how to make such reaction in a safe way,
>>and which kind of tube may resist to such pressure?
>>
>>Regards
>>
>>Bel
>>
>>
>>
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>Institutes for Applied Research
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Prof. Jacob Zabicky
Institutes for Applied Research
Ben-Gurion University of the Negev Private: POB 12366, Beer-Sheva 84863
POB 653, Beer-Sheva 84105, ISRAEL Tel. +972-8-6496792
http://profiler.bgu.ac.il/site/main.cfm
Tel. +972-8-6461271/6461062/6472754
Fax. +972-8-6472969
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