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Author: Subject: hydrogenation
Hazard to Self

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[*] posted on 23-2-2011 at 12:07

Being a novice chemist, I heard that hydrogenation is a dangerous process for first timers, as you have to flush with nitrogen and make sure your experiment is void of air.

I'm working on making a small scale synthesis of ethidium bromide via the paper I attached by De Nobrega Bastos and Mahler.

My question is out of caution, the part that I'm most worried is bubbling H2 through a fitted flask for 40 minutes. The reaction vessel is very small, the catalyst is 0.2 g platinum oxide. The solvent is acidic ethanol 5ml. All this is done while maintaining reflux.

Do I need to take the typical hydrogenation precautions for this experiment and flush out the reactor, or just slowly bubbling it through for 40 minutes will be okay?

Attachment: de nobrega.pdf (372kB)
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[Edited on 2-23-2011 by andre178]
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[*] posted on 24-2-2011 at 09:16

I wouldn't worry too much. PtO2 in and of itself is not too prone to fires, what happens is in situ it is reduced by hydrogen to platinum black which is the active catalyst.

That being said, I think you could get away just vigorously stirring the stuff under a balloon of hydrogen in a hydrogen flushed flask. I have found PtO2 and 5% Pt/c to be quite active catalysts for the reduction of aromatic nitro groups at atmospheric pressure. I think the conditions in this paper are really overkill.

Just a heads up, before you run the hydrogenation you should take care to have a very pure product. Hydrogenations are very sensitive to poisoning.
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