Free-Energy Relationships for Substituent Effects

Linear Free-Energy Relationships for Substituent Effects 

The experimental KIE can be compared with KIEs calculated from transition structures on the basis of the vibrational frequencies associated with specific bonds. This information is available from computed transition structures, and the comparison can provide a direct experimental means of evaluating the computed transition structures.The method has also been used to measure KIE in reactions such as the bromination of pentene and epoxidation of propene. Those transition stmctures that are inconsistent with the observed KIE can be excluded. 

---