Table 2 Enthalpies (∆H) and free energies (∆G), barrier energies \(\left( {{\text{E}}^{\text{f}}_{\text{a}} ,{\text{E}}^{\text{b}}_{\text{a}} } \right)\), relative energies (∆E) computed at 298 K of the stationary points involved in the studied 13DC reaction using B3LYP/6-311 ++G** level of theory