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Lakshanna Yogarathnam

Why use sulphuric acid in preparation of aspirin?

Don Eamon  Follow

The acid serves to protonate one double bonded oxygen on the acetic anhydride this makes the reaction with the salicylic acid faster. The proton is returned to the acid in the end,

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Benjamin van As  Follow

You are most likely preparing Aspirin from salicylic acid and acetic anhydride.

This esterification reaction is catalysed with small amounts of a strong acid. (sulfuric acid in this case)

If you add more than catalytic amounts, the sulfuric acid itself would hydrolyse the aspirin back to salicylic acid and acetic acid.

If you were to add very large amounts of sulfuric acid you might even sulfonate acetic anhydride to sulfoacetic acid.

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Bipolar & Mood Disorders  Follow

The acid serves to protonate one double bonded oxygen on the acetic anhydride this makes the reaction with the salicylic acid faster. The proton is returned to the acid in the end so it is just a catalyst. Here is a reaction scheme done using phosphoric acid but the mechanism would be the same with sulfuric acid.

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David Bell  Follow

Depends on how you were running the reaction.

You could make aspirin from salicylic acid and acetic acid, using sulfuric acid as the catalyst. Without it, the reaction would not proceed at a useful rate.

But you can also make aspirin using acetyl chloride or acetic anhydride rather than acetic acid. In these reactions, sulfuric acid is not needed to catalyze the reaction.

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Chris Mansker  Follow

Sulphuric acid is used as catalyst for the reaction between salicylic acid and acetic acid to form acetylsalicylic acid/ asprin.

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Daryl Storey  Follow

Salicyclic acid reacts with acetic anhydride under acidic conditions to form acetylsalicylic acid (Aspirin) and acetic acid (Acid catalyzed reaction).

The functions are

Salicyclic acid, acetic anhydride - reagents

Sulphuric acid - catalyst

The reaction being

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Benson Flory  Follow

Sulphuric acid is used as the catalyst.

The sulphuric acid is not used in the reaction, it is just used as an acid catalyst of the esterification process.

See: mechanism for the esterification reaction

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Digital Tech & Business Innovation  Follow

It is the go-to catalytic acid. HCl is volatile, HNO3 is a powerful oxidizing and nitrating agent. Hard to beat sulfuric (But options do exist).

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