Understanding the Isomerization of Monosubstituted Alkanes from Energetic and Information-Theoretic Perspectives

A unified explanation for the relative stability of linear and branched alkanes is still lacking, and research in this direction is ongoing. Unlike the conventional orbital-based description, we have employed the density functional theory (DFT) based on the total energy and its components as well as a newly proposed energy partitioning scheme [Liu, S. B. J. Chem. Phys. 2007, 126, 244103]. Taking monosubstituted hydrocarbons CnH2n+1-R (n = 3, 4, 5, 6; R = OH, OCH3, NH2, NO2, F, Cl, CN, CHO) as examples, we have investigated the molecular origin and nature within the framework of the DFT. Our computational results revealed that no such a single energy component that dictates the transformation of the mono-substituted alkane derivatives. By the binary fit of the electrostatic potential and steric hindrance from the new energy decomposition scheme, we unraveled that isomerization is mainly governed by the electrostatic potential, while the steric effect has a minor influence. Moreover, we established a linear relationship between the Shannon entropy difference and the Fisher information difference, which is accordance with previous findings. Further, there was no linear relationship between E-e and the Fisher information or Shannon entropy.