Question- After collecting a first crop of norbornene-5,6-dicarboxylic anhydride, TLC indicated the prescence of a further product in the mother liquor. The solution was concentrated on the steam bath to isolate a second crop of product, but the residue proved to be an oily liquid, and the desired product could not be crystallized. Suggest the reason for the problem. What was the oily liquid?
If possible just a brief explanation how you got the answer?