In this work, five substituted 2'-Hydroxychalcones were prepared using Claisen - Schmidt condensation which were used then as a synthone for substituted flavanones via base catalyzed isomerization. The latter process has been studied kinetically in order to determine the rate constant. These experiments were performed using HPLC technique in (8:2) (CH3CN:CH3OH) medium at different temperatures (298 K - 318 K). The obtained results were interpreted by a four-step mechanism which considered the existence of phenoxide ion as the key intermediate.
The main reaction was achieved as a pseudo first order reaction in which the rate of the studied compounds followed the sequence 1>2>3>4>5, and the activation energy had the same sequence for these compounds. The reaction rate was affected by the electronic behavior of the different substituents at ring B since they played an important role in the stability of the intermediate that led to the final product.