Application of numerical basis sets with a family of DFT methods to predict the transition states of Diels-Alder reactions: Assessing the accuracy through synchronous transit method

Knowledge of the transition state is crucial in determining the mechanism in order to diversify the applicability of the reaction. The computational method is the most convenient way to locate the transition state in the absence any efficient experimental technique. We have applied the method of the transition state search on the Diels-Alder reaction computationally by means of combined linear synchronous transit and quadratic synchronous transit methods. Here we have shown that, of various methods adopted, BOP functional with numerical basis set provides a computationally economical alternative to the widely used B3LYP functional with higher Gaussian basis sets in the transition state search. It can reproduce the experimental parameters like activation energy of the Diels-Alder reaction, and the calculations are much faster than the corresponding other functional based calculations.