Dear Colleagues,
I met some problem recently when i tried to acetylate  an amine compound
namely, 2,5 Dimethoxyaniline.Below were some of the ways that i've
attempted:
1)Dissolved the amine( used as newly received-but there's lots of black
stuff in there) in acetic anhydride and refluxed for 1-2 hrs (color of
the solution turned brownish)and let cool before pouring into
water.boiled to evaporate off the acetic acid.
observn.: no precipitate.
2)Dissolved the amine (purified by sublimation) in acetic
anhydride,added two drops of conc sulphuric acid and refluxed for 1-2
hrs and let cool before pouring into water.Boiled to evaporate off the
acetic acid.
observn:no precipitate, but the it couled be precipitated with acetone
to give some brown solid.
3)Dissolved the amine (not purified) in acetic anhydride,added two drops
of conc sulphuric acid  and left there for 1hr before pouring into warm
water.Boiled to evaporate off the acetic acid.
obsern: no precipitate
Question:
1)Can anyone please suggest to me the actual problem that's taking
place?
2)The aniline was suppose to be 98%+ pure but why is it giving me so
much of black stuff?
Thanks in advance.

Regards,
Barnabas


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