BENZENE IS NOT VERY RIGID

The concept of molecular kurtosis as a dynamic molecular shape descriptor is introduced and used to compare the relative flexibilities of benzene and cyclohexane. For small torsional deformations (<15-degrees) the potential energy surfaces are similar, indicating both molecules are flexible. Using molecular kurtosis, the stiffness of benzene and cyclohexane are compared from gas-phase stochastic dynamics simulations and validated by distributions found in the Cambridge Structural Database.