Question

How is unreacted acetic anhydride removed from the aspirin product?

Answer 1

Answer:

After the formation of aspirin product i.e (aspirin + unreacted acetic anhydride) water will be added. This converts any unreacted acetic anhydride to acetic acid. Aspirin is not very soluble in water. So, it crystallizess as the solution cools. It is then isolated by vaccum filtration. Most of the acetic acid is removed by filtration. but enough remains to heavily contaminate the product. the product purified by recrystallization in hot water. This removes most of the remaining acetic acid.

In this way we can remove the unreacted acetic anhydride removed from the aspirin product.