[OrganicPupil]

Hello,

I had a question about the reactivity of cyclic anhydrides. I'm trying to understand why in the reaction,"
Reaction of 2-benzofuran-1,3-dione with excess NH3" the anhydride doesn't continue to react and in this reaction, "Reaction of 4H-2-benzopyran-1,3-dione with HCl" the anhydride reacts completely.

Thanks

[AWK]

?
Phthalimide can be prepared by heating phthalic anhydride with aqueous ammonia  with good yield.