Propafenone is a well-known anti-arrhythmic drug. During the synthesis of Propafenone some structurally related compounds are formed as impurities which is to be identified, since some of the impurities formed may decrease the activity or a threat to the usage of the drug. So characterization of such impurities very much needed for better therapeutic index. One such impurity is (2E) - dehydro propafenone hydrochloride which is synthesized by aldol condensation.