amrhamed2
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Sulfonation of 4-nitroaniline
Does anyone have experience with such reaction?
Well I will tell u my own experience
1-This reaction proceeds at 140 degree to give 2-amino 4-nitrobenzenesulfonic (example of procedure 2 gm 4-nitroaniline and 4 ml conc sulfuric and
heating at 140 degree)
2-My bad experience is with scaling up ...when I used 50 g of 4-nitroaniline and 100 ml conc sulfuric ,boiled over drastically though I have added
4-nitroaniline over 2 hours to warmed sulfuric acid (at 70 degree)
I wonder what happened and what to do to avoid that
amr h mahmoud
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amrhamed2
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I really need help in that reaction
amr h mahmoud
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panziandi
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sounds like with the scale up the heat of the reaction is not disipating away from the locality and causing local over heating. Are you stirring the
reaction mixture with an overhead? Perhaps lower the temperature. Nitrations and sulphonations are very prone to runaway reactions. Sulphonations can
sometimes lead to local charing if not well moderated have you seen this? Is the 4-nitroaniline dry? If it contains water at all, adding something
moist or carrying water into warm sulphuric acid will be devistating! Try a scale up in between the two, often scale up reactions require different
conditions.
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amrhamed2
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thanks man but the strange about my trial is that things went wrong after 3 hours at the same conditions
I tried sulfonation of 10 grams using 50 ml conc sulfuric and things went well ....is that logic as I used 50 ml instead of 20 ml ?
I really hope to see an appropriate literature procedure for an amount of 50 gram or more
amr h mahmoud
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panziandi
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Perhaps when you ran it with extra sulphuric acid the extra acid acted to disipate the heat by absorbing it. Perhaps more acid is necessary? If I was
doing the reaction I would add the nitroaniline to the pre-cooled acid and stir vigorously then allow the acid to cool again before adding the next
portion of the nitroaniline (portions would be say 1/10ths of the aniline used to see how warm it gets and adjust if needed). Then I would allow it to
warm up and finally heat with stirring if that is needed (follow what your method states). I haven't checked your quantities but you will want H2SO4
to react with the NH2 group to solvate (1mol acid to 1mol base) you will want H2SO4 to sulphonate the ring (1mol acid to 1mol ring) and you will want
an excess of sulphuric acid to solvate (I don't know what volume). Make sure you thus have >>2mol H2SO4 per 1mol nitroaniline.
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