[lily1998]

Hi,

I am currently taking preparatory reading for a research that i plan to do.My topic is on organic chemistry - Aspirin to be precise.And my investigation question is "Which catalyst and how much of it would give the highest yield of aspirin ?" The catalysts are phosphoric and sulfuric acid.

I am aware that catalysts are used to speed up and provide an alternate route for the reactant particles to react thus resulting in more successful collisions. But at the same time from what i have learned in school the use of catalysts has no effect on the yield of a reaction.I am having doubts on whether it is the right question to ask. Can a catalyst increase the yield of a reaction?

[Arkcon]

By the classical definition of catalyst, you are correct.  If this isn't a seriously screwed up assignment,we have to try to figure out what is meant.  Maybe the acid isn't just a catalyst?  You'll have to look this up and see.

[lily1998]

The starting material , ethanoic anhydride, which is also in excess is protonated by the catalyst and makes it more reactive.So i suppose the research question is applicable?

[AWK]

Catalyst does not increase the yield of reaction. Organic chemists often use
p-toluenesulfonic acid as catalyst, but in synthesis of aspirin the better catalyst are sulfuric and phosphoric acids. This is a 150 year experience.
Concentrated sulfuric acis is much more dangerous chemical than 80 % phosphoric acid used in this procedure but most students cannot explain why relatively weak phosphoric acid work as catalyst as if it would be a strong acid in this reaction.

[lily1998]

Thank you so much.