RobRylan - 9-1-2016 at 06:51
Hello!
I was recently extracting acetylsalicylic acid from aspirin tablets using ethanol and was evaporating the ethanol off the crystals. I think probably
heated it too high but whatever.
As the ethanol evaporated an extremely pungent odor began to come off so I took it off heat and let it cool. The crystals were dry enough now but I
noticed something odd. Along with the normal smell of aspirin there was a faint wintergreen odor.
Is it possible that the aspirin decomposed into salicylic acid and acetic acid and then further react with the ethanol to form ethyl salicylate? How
might the acetylsalicylic acid have decomposed into its constituents?
DrMethyl - 9-1-2016 at 07:04
Hi,
Methyl salicilate will be probably present because of the wintergreen smell but remember it's a liquid and you get a solid, you probably have small
impurities (Me Salicilate), so you can recrystallise your product in a suitable solvent or wash your crystal with, I think, a very apolar solvent
which dissolves Me Salicylate and not the acid such as i.e. petroleum ether.
Washing will be sufficient IMO, let dry the crystals after crystallisation/washings and check with your nose.
Don't forget Me Salicilate is a very potent odor, a few mg is sufficient to give a pugnent smell.
RobRylan - 9-1-2016 at 07:49
Thanks for the response. I forgot that the ethanol I was using is denatured so it would have methanol.
UC235 - 9-1-2016 at 16:56
Ethyl salicylate smells almost the same as the methyl ester. No need to invoke methyl salicylate. As your ethanol certainly contains some water due to
it's hygroscopic nature, hydrolysis of the fairly sensitive phenyl acetate ester to salicylic acid is unsurprising.
If you're looking to recrystallize/extract aspirin from tablets without changing anything, I recommend hot acetone. Clean aspirin is odorless but it
tends to take on the smell of acetic acid from interaction with moist air.
[Edited on 10-1-2016 by UC235]
semesa - 9-1-2016 at 21:10
If esterfications occured that easily there'd be no need to use catalysts.
Did it smell anything like pyridine?