Re: ORGLIST:Bromination

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From: Darren Rhodes (drhodes$##$globalnet.co.uk)
Date: Thu Aug 08 2002 - 08:15:29 EDT


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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