[Fieldy]

Hi All, This is my first post, so please excuse my noobiness.

I have 1g of di-acid (cis-norbonene-5,6 endo-dicarboxylic acid) to which 5cm3 sulphuric acid is added. The solution is heated for around a min until the di-acid dissolves, then cooled in an ice bath. To the solution, pieces of ice are added until there's roughly 30cm3 of solution.
       It's an experiment we've been given to identify 'compound x', which is a structural isomer of the di-acid.
           
 When the sulphuric is added it should convert the di-acid to its anhydride. Then when the ice/water is added, surely this should convert the anhydride back into the di-acid. The only thing I can think off is the reaction is very slow (hence the ice bath) and that compound X is an intermediate of some kind.
      I've got through half a notebook of scribbled mechanisms trying to figure it out, but I'm stumped. Im not looking for the answer, but If someone could point me in the right direction it would be hugely appreciated.

Thanks in advance.

F*

[orgopete]

Well, it could be something as simple as lactonization or it could be the exo-diacid via a retro and forward Diels Alder reaction, see http://thesis.library.caltech.edu/3926/

[Fieldy]

I think it is just the lactonization, thank you for your help, and the link.

F*