Estimation of the racemization rate constants for α-amino acids using Density Functional Theory

This research shows that the Gibbs free energy, which is calculated by Density Functional Theory (DFT), largely deviates from the experimental value, but is proportional to the experimental value. Moreover, the slope and intercept are equivalent between molecules within the same class, such as a-amino acids. Based on this conclusion an efficient and reliable protocol is presented to estimate the racemization rate constants (k(rac)) of a-amino acids using DFT at the level of B3LYP/6-311G(d,p). The polarizable continuum model (PCM) is used to describe solvation when the calculation is completed in aqueous solution. In this way, 21 racemization rate constants (k(rac)) are reproduced with the maximum deviation of 0.601 log(k(rac)) unit, and the standard deviation of 0.267 log(k(rac)) unit. The calculation results indicate that the data estimated by this approach gives a fairly good fit with the experimental results. (C) 2017 Elsevier B.V. All rights reserved.