[dnb]

hi people,

my question is related to the following reaction:

anilide +  ac. sulf. +  ac. nit. +  ac. acetic glacial  =>  p-nitroanilide + H20 +
ac. acetic glacial  +  ac. sulf.


i don´t get how ac. acetic glacial fits in the "classic" mechanism of that kind of nitration.


Please, send-me the mechanism and an reference of where the mechamism was taken

thanks...

[shelanachium]

I presume you mean:

Aniline + sulfuric acid + nitric acid + glacial acetic acid ---> p-nitroacetanilide.


The glacial acetic acid is not a catalyst but a participant. The first step is the formation of acetanilide by:

C6H5NH2 + CH3CO2H --> C6H5NHCOCH3 +H2O; the sulfuric acid acting to remove the water. I think acetanilide is more usually made by reacting aniline with acetic anhydride:

C6H5NH2 + (CH3CO)2O --> C6H5NHCOCH3 + CH3CO2H

I think you might have trouble using concentrated sulfuric acid + acetic acid because the aniline will be protonated to [C6H5NH3]+ which is unreactive to nitration or substitution of an acetyl group on N.

The next step is nitration of the acetanilide to p-nitoacetanilide:

HNO3 + 2H2SO4 --> [NO2]+ + [H3O]+ + 2[HSO4]-

Followed by [NO2]+ + C6H5NHCOCH3 + [HSO4]- --> p-O2NC6H4NHCOCH3 + H2SO4

Acetanilide is much less basic than aniline so is not totally converted to an unreactive cation by concentrated sulfuric acid.

You will find the mechanism of nitration of aromatic compounds like this in any elementary organic textbook, also try googling 'aromatic nitration mechanism'.