Further examination of the BEBO model with the results of ab initio calculations of a reaction series Original Research Article

The BEBO (bond energy-bond order) model is further examined with results of ab initio calculations on a series of metathetic reactions involving hydrogen transfer. Energies are calculated at the 6–31G∗∗/PMP2=full/6–31G∗∗ level while the bond-orders are estimated using the 6–31G∗∗ basis set with the geometry optimisation at the single configuration unrestricted Hartree-Fock frame. Our analysis reveals that for all thermoneutral reactions where the making and breaking bonds are collinear in the transition state, the reduced distensions in the transition state structures are same and independent of the bond-order exponent in the BEBO model. For others such displacements increase with the square of the energy changes during reactions. The Bronsted coefficient is examined and is found to be neither strictly parallel to the position of the barrier in the reaction path nor a measure of the ‘transition state’ structure of the system.