Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Rory on May 26, 2006, 04:22:10 AM
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hi all,
In class today we were synthesizing aspirin by mixing salicylic acid and acetic anhydride with a sulfuric acid catalyst. One of the things I have to do for the prac writeup is describe how to prove that the sulfuric acid isn't a reactant - I have no idea how to prove this. ???
You can't do it by testing pH or titration or anything because both a reactant and a by-product are acidic, so they would interfere. And gravimetric analysis won't work because it's impossible to measure the mass of sulfuric mass both before and after the reaction. i thought maybe doing the reaction without the sulfuric acid present to show that the reaction still occurs (albeit very slowly) without it present. Any ideas or comments?
Cheers, Rory
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How about looking for the S=O stretch in the IR?
The more direct experimental way would be to use a catalytic amount of H2SO4 and see if you get catalytic turnover, although that doesn't give direct evidence for the presence of the catalyst after the reaction.
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You may precipitate H2SO4 with BaO solution(barite water) as BaSO4. Yse stechiometric Ba2+ to SO42- to avoid possible side reaction with acethyl salicilic acid thow i think its not very prone.After filtration BaSO4 and drying you may gravimetrically prove H2SO4 as catalist.