[sharbeldam]

I know its a strong base, so does it take the hydrogen on the right side of the ester? to make a condesation reaction with the other esteR? also if it's condensation (Claisen), after i add the H3O+ , does it split the ester ring to give OH?

- edit: the second photo is my product but it doesnt seem right according to the number oF H

[kriggy]

Your product is wrong, its missing one OH group - the lactone is cleaved into COOH and OH, therefore you are missing an OH group. Does it matcht he elemental formula of your product? If not, then its likely the ring is still closed after the addition of acid

[sharbeldam]

You are right, the ring is still closed, but what are the rules about when rings open when we add acid? how am i supposed to know that the rings stay closed after the addition of the acid and when they open? I'd also be happy if someone recommends a book that explains this reaction deeply and others similar to it.

[kriggy]

Its IMO different in each specific case. We can argue that 5 or 6 membered rings are more stable than smaller or bigger rings but I dont know any specific rules you can use. I think usually, heating or long reaction times indicate ring opening while just simple acidic workup is without ring opening