Maggie
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nitration
Can someone help me with mononitration of p-methoxy phenol in o-position?
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unionised
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Which o position o to OH or to OCH3?
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The OCH3 is also activating and o-p directing. Specific o nitration would be a pain in the neck; you will get both isomers. Once you have a nitro
group on the molecule it will be rather less reactive so mononitration might not be too difficult.
You could get more specific nitration by deprotonating it, (O- is a much better activating group than OMe or OH), reacting with a diazonium ion in
basic conditions, reductive cleavage of the N N bond and then oxidation of the amine to give a nitro compound but the yield would be lousy,
particularly at the last stage.
Why do you want to nitrate the stuff?
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Geomancer
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In a paper "Nitration of Phenols Under Mild and Heterogeneous Conditions" M. A. Zolfigol et al. claim to have done this in 84% yield using
Mg(HSO4)2 and NaNO3 on wet SiO2 in DCM. The reaction appears general for phenols and suitable for amateur use.
The work was published in the online journal "Molecules" 2001, 6, 614-620, available from http://www.mdpi.org.
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Maggie
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I have tried the magnesium bisulphate process given by Zolfigol, but without success.Does anybody has practically worked on mononitration of phenols?
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Maggie
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nitration
I have followed the experimental procedure given in the paper and the product after reaction completion,which I have isolated,purified and
characterised by GC-MS turned out to be a dinitro compound. I have tried other reagent i.e. sodium bisulphate with similar results.
I have also tried changing reaction parameters viz.temp. solvent, mode of addition etc. but the results are not encouraging.
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Geomancer
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Interesting. Are you saying that the procedure prefers substitution on the mononitro compound to the original? If so, do you have any theories as to
why this happens, seeing as the nitration product should be less electron rich?
Seeing as Zolfigol specifically mentions this compound, you should probably discuss your difficulties with him, as well.
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Maggie
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nitration
Yes!It is really very interesting that formation of dinitro is preferred over mononitro compound,as presence of one nitro group is supposed to
deactivate the ring to some extent.But, right now I cant think of any other explanation than that its the two groups -OCH3 and -OH, para to each
other,are playing the trick,making the ring active enough for the dinitro to be the major compound.Anyway its a good suggestion to interact with
Mr.Zolfigol himself.Thanks!
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