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Topic: What is the formula of this?  (Read 2223 times)

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Offline NaOH

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What is the formula of this?
« on: February 05, 2010, 09:13:18 PM »
I saw this video and I was wondering what is the formula of the "bromine" they use.

http://www.youtube.com/watch?v=hVK9Om4wzBM

Isn't bromine liquid why is that solid.

Offline Dan

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Re: What is the formula of this?
« Reply #1 on: February 07, 2010, 06:17:44 AM »
Yeah, bromine is a volatile brown/red liquid which appears to be generated during the reaction.

That solid is probably this stuff: http://en.wikipedia.org/wiki/BCDMH

Which is sold as swimming pool disinfectant, and is a source of HOBr and HOCl.

I suspect we have something like this going on.

The alcohol is oxidised by HOBr.

HOBr + RCH2OH ----> RCHO + H2O + HBr
HOBr + RCHO    ----> RCO2H + HBr

This is generating HBr. Mixtures of HBr and HOBr can generate bromine.

HBr + HOBr <-----> Br2 + H2O

The bromine can then go on to oxidise the alcohol directly (this is why the solution is colourless at the end of the reaction), and some is lost as bromine gas due to the heat generated.

The HOCl present can do similar reactions, but also oxidises HBr to bromine (as will any Cl2 generated in the reaction):

2HBr + HOCl ----> Br2 + H2O + HCl <----> HOBr + HBr + HCl
« Last Edit: February 07, 2010, 06:53:19 AM by Dan »
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