The first two terms are related with stretching motions describing, respectively, the six equivalent C-H bonds and the C-C bond in ethane. Vstr is developed as the sum of six London-Eyring-Polanyi functions while VCC is described as a Morse function. They depend on 26 and 3 adjustable parameters, respectively. The following two terms describe bending motions associated with the ethane-ethyl transformation in the reaction. Vbending is developed as the sum of harmonic terms, where the angles associated to hydrogen atoms bonded to C1 and C2 were separated to treat independently both methyl groups, equivalent in ethane, which evolve towards -CH3 or -CH2 non-equivalent groups in the ethyl product. This term depends on 22 adjustable parameters. Vop is developed as a quadratic-quartic potential and was included to reasonably simulate the change from the pyramidal (-CH3 group) in the reactant to the planar (-CH2 group) geometry in the product. Only 6 adjustable parameters were necessary to define this term. Another important nuclei motion in this reaction is related with the torsion around the C-C bond between the two methyl groups. To describe this motion, the Vtor term is included, which depends on 3 adjustable parameters, describing the torsional barrier height and the torsional angle in ethane. Finally, the VHCN potential is included to describe the HCN product, depending on 6 adjustable parameters. This term includes the new CN stretching motion, which is defined as a Morse potential, and the HCN bending motion, which is described as a harmonic term taking as reference angle the lineal HCN (180º) structure.