We further demonstrate the applicability of the ACE MLPs by employing them to compute free energy contributions for the reaction between MVK and CPD, R3. These contributions are often calculated within the rigid-rotor-harmonicoscillator (RRHO) approximation. However, this method is known to be inaccurate for the description of low-lying vibrational modes. To overcome these limitations, different static approaches have been developed. They include the method introduced by Truhlar, referred here to as shifted RRHO (sRRHO), where all low frequency harmonic modes below a threshold are shifted to that value and the qRRHO method introduced by Grimme, where those modes are treated between harmonic vibrations and rigid rotors. Using the ACE-MLPs trained for this reaction at the PBE0-D3BJ/def2-SVP level of theory we computed the free energy profile for R3 using umbrella sampling (MLP-US) over an averaged reaction coordinate, r = (r 1 + r 2 )/2 (Fig. ). This approach enabled us to fully sample the different conformations not only at the critical points but along the reaction pathway, totalling 1.5 ns of sampling, which would be impossible to reach with AIMD. Moreover, our MLP-US simulations also capture anharmonic effects arising from low vibrations modes, which are not directly accounted for using the static methods. The MLP-US also provides a piece-wise free energy, where the choice of reaction coordinate is flexible.