thanks for your help
I've done some research on tautomerism, and one of the websites that i've looked at says that it is catalysed by an acid or base. But if the acid is PCl5 which only acts as an acid in water, is it still possible that when pcl5 reacts with a liquid ketone (which is normally a liquid at room temp) that pcl5 reacts with the ketone to become an acidic solution. Then is this acid that catalyses the tautomeris
ie pcl5 + 4H2O = H3PO4 +5HCl