Keras
International Hazard
Posts: 1143
Registered: 20-8-2018
Location: (48, 2)
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Para amino-acetanilide
Folks,
because I had a few grams of acetalinide I made while testing the synthesis without acetic anhydride, and I didn't know what to make of it, I decided
to go ahead and make paracetamol in a rather winding way:
acetalinide → para-nitrosoacetanilide → para-aminoacetanilide → diazonium salt → paracetamol.
For the sake of brevity, I won’t detail all the steps, unless you want me to spell them out. In any case, I’m just halfway through it and I have
obtained some very nice, pristine white crystals (see picture), but I’m not sure they are para-aminoacetalinide. I fear they might be:
– Unreacted acetalinide (although they don’t really look the same).
– Sodium acetate (I had to use acetic acid to dissolve acetalinide for the nitrosation, and later to neutralise the pH after it).
Apart from going on, try and diazotise them, what could I do to ascertain their nature, given that I can’t measure their melting point?
Also, this is unrelated. I found that the sodium nitrite I used for nitrosation, and that stands on my shelf home for two + years, had become grey.
When dissolved, it produces a slightly greyish mixture, with a bunch of tiny black dots floating. It looks like dust, but it isn't, since the bottle
was capped at all time. What kind of impurity can it be?
[EDIT] Since that message I filtered the mixture and obtained a batch of white fluffy crystals with a very faint, but I think characteristic smell of
what I classify as ‘aromatic amines’. It’s difficult to characterise, but it’s about the same as para-aminophenol. Vaguely fishy, soapy maybe.
Seems a good omen. In any case, not at all related to nitro compounds (as I experienced them).
[EDIT 2] So the crystals are now more or less dry, I weighted them and got 2.35 g, which is of course impossible since I started with 1.35 g of
acetanilide, i.e. 10 mmol. p-aminoacetanilide has M = 150 g/mol, so… there’s definitely 850 mg of something else in these crystals (or maybe
remaining water? Water of crystallisation? Some hydrate form? Sodium acetate?).
[Edited on 28-9-2025 by Keras]
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