Paulo
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Benzene nitration by-products
I’m a PhD student and I’m studying the benzene nitration process under industrial conditions.
This is a heterogeneous liquid-liquid reaction where the benzene reacts with nitric acid to produce mononitrobenzene (MNB) and the sulphuric acid acts
as catalyst to form the nitronium ion (NO2+). The range of temperature is between 80-130ºC.
One problem of this reaction is the by-products formation, namely the nitrophenols (NP’s), dinitrophenol (DNP) and trinitrophenol (TNP) which are
identified. The oxidation of benzene into phenol it seams to occur in the acid phase, while the nitration occurs in the aqueous phase.
When I’m doing HPLC analysis, another non-identified peak appears which I couldn’t yet correctly identify.
The questions I want to make are:
1. It is possible during the benzene oxidation into phenol to form resorcinol?
2. Will this resorcinol nitrate into dinitroresorcinol (DNR) or trinitroresorcinol (TNR)?
3. Another problem is that I can’t find any supplier of DNR or TNR, anyone knows why?
Any help on this matter will be a great help.
Thanks in advance.
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madscientist
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1. I can't think of any reason why that wouldn't occur. I doubt anything oxidized beyond resorcinol is going be very stable, so I think the
mystery compound likely wields two OH groups on the aromatic ring, as you suggest.
2. Yes.
3. This I'm not really sure of, but perhaps because they're not very useful laboratory reagents and are dangerously explosive?
I weep at the sight of flaming acetic anhydride.
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Polverone
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another guess for 3:
Not very much demand (okay, that still doesn't explain why Sigma-Aldrich wouldn't have it) and trivial to synthesize from resorcinol.
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Marvin
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A few random thoughts,
How many dinitrophenols have you identified?
How many trinitrophenols?
How pure is the benzene used for the test, how much toluene in it, anything else?
Have you detected any benzene sulphonic acid compounds?
How about degredation products of the benzene ring?, 4 carbon anhydrides/caboxylic acids? Oxalic acid?
I would be inclined to try some wet work, extracting the residue with alkali/analysing the remainder, and then selectively precipitating acids by
slowly changing the pH. I dont think in this case it will result in pure seperations, but in combination with HPLC it should give you a better idea
what unidentified peaks in the main experiment correspond to particulaly if they are carboxylic acids/sulphonic acids/phenols. The temptation is to
get a decent sample and run it through a mass spec. Will the HPLC setup you are using allow you to take off samples from what is currently running
out of it?
[Edited on 14-9-2003 by Marvin]
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squeeker50
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If I may...
If I may interject a simmilar question, that unfortunatly would help me and not you....I am still an undergrad and working on a lab project. I have
been trying to find the best way...or any way at all, to brominate nitrobenzene. I have found references to one method used that calls for an
involved procedure that I do not have to ability to do. It was too long (I have 2 periods of about 3hours) and required chemicals and apparatus my
school does not have.
I thought that this was slightly similar to your discussion and I didn't know if anyone had any ideas of how to do this or where I could look.
Any help would be greatfully welcomed.
Thanks!
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unionised
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Strange as it seems, trinitro resorcinol is (occasionally) used as a reagent. Like picric acid it forms crystaline complexes (charge transfer IIRC)
with aromatics.
Have you tried looking for it by its other name "styphnic acid"?
This sort of thing is a bit obscure these days, nobody measures a melting point, they put the stuff through a mass spec.
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