Keto‐enol tautomerism from the electron delocalization perspective

Abstract

The equilibrium between keto and enol forms in acetylacetone and its derivatives is studied using electron delocalization indices and delocalization tensor density. We demonstrate how electron delocalization governs the equilibrium between keto and enol forms. The less stable enols have more distinct double and single bond character in the C C C fragment, while electron delocalization in this fragment is more pronounced in more stable enols. Looking for the origin of such behavior, we considered the one-electron potentials entering the Euler equation for the electron density. We found that electron delocalization is mainly governed by the static exchange potential, which depends on the three-dimensional atomic structure. It, however, does not distinguish differences in electron delocalization in more and less stable enols, the effect arising from the kinetic exchange contribution, which reflects spin-dependent effects in the electron motion. The local depletion of kinetic exchange in the conjugated fragment yields the enhanced electron delocalization along the C C C bonds in more stable enols. Thus, a combination of considered descriptors allowed us to reveal the influence of electron delocalization on the equilibrium between keto and enol forms and showed the significant features of this phenomenon.

DFT potentials from a chemical perspective: Anatomy of electron (de)localization in molecules and crystals

“…We can conclude that fermionic potential proved itself as a sensitive tool for studying electron delocalization changes caused by the chemical modifications and influence of the crystal packing and the geometric parameters of the unit cell. This perfectly agrees with our previous experience of its use in small molecular and large biomolecular systems 79,105 . The current work clearly demonstrates that the ability of the to take into account all physical effects responsible for electron delocalization is crucial for reliable description of this effect.…”

“…previous experience of its use in small molecular and large biomolecular systems. 79,105 The current work clearly demonstrates that the ability of the v f to take into account all physical effects responsible for electron delocalization is crucial for reliable description of this effect.…”

“…The DFT functional impact on the features were examined previously (see SI of Reference 105). Briefly summarizing our findings, we can recommend use of the hybrid functionals (including range‐separated functionals) for electron (de)localization studies.…”

Electron delocalization in defect-containing graphene and its influence on tetrel bond formation

“…It has a physically intuitive interpretation: the wells in the v f (r) distribution correspond to the domains of maximum electron localization in the system (classically allowed areas), while the potential's barriers prevent delocalization of electrons through them (can be penetrated via tunnelling). This descriptor has already shown itself as a powerful tool for electron (de)localization studies in molecules, crystals, and macromolecules [46][47][48][49] and we suggest applying it now to the 2D periodic systems such as the defected graphene layer. We will demonstrate that the tools we offer for electron (de)localization estimation are useful for assessing the attenuation of a defect influence on a graphene surface.…”