Isomers of Alkali Metal (Methylbenzyl)allylamides: A Theoretical Perspective

Abstract

Recent studies of alkali metal N-(α-methylbenzyl)allylamides containing lithium, sodium, and potassium have shown unique rearrangements in NMR experiments. It was found that lithium isomers favored the formation of aza-allyl and aza-enolate complexes that could exist in a solution for a substantial amount of time. As the radius of the metal ion increases going from lithium to potassium, so does the preference for the formation of the imine structure. For sodium, the aza-allyl complex could still be isolated, whereas the imine structure was only found to be stable on the scale of several hours for potassium. In this work, ab initio calculations were used to shed light on this phenomenon. Decomposition of intermolecular interaction energies of the aza-allyl, aza-enolate, and imine complexes showed that for lithium, the formation of aza-allyl and aza-enolate complexes was driven by electrostatic interactions. For potassium, the dispersion component of the metal interaction with the ligand proved to be more important for the stability of the imine structure. The presence of the imine formation in potassium and partially in sodium was found to be due to the reduced electrostatic nature of these larger metals. The assignment of the experimental NMR spectra was further confirmed with the natural bond order (NBO) analysis as well as the partial charge calculations. Analysis of orbital energies, specifically those of the highest occupied molecular orbitals (HOMOs), as well as the deformation energies of each of the ligands, were also considered. Through these procedures, an understanding of the tendency for each metal to have a unique isomerization pathway was gained.

Hydrocarbon Soluble Alkali‐Metal‐Aluminium Hydride Surrog[ATES]

“…Notably the increase in the LDF is particularly significant at the lithium sodium junction. These results follow a similar pattern to the one reported by Izgorodina and co‐workers in a study focusing on the stability of different isomers of a series of Li−K N‐(α‐methylbenzyl)allylamides [38] . We find that as ion sizes decrease the magnitude of electronic interaction energy decreases due to higher charge density, while dispersion attraction energy increases with ion size due to the distances of the outer electrons to the nuclei.…”

Thermodynamics of Tri- and Tetraepoxyimidazolium NTf2 Amine Polyaddition: A Theoretical Perspective

“…Water was chosen to emulate the highly polar local environment given by the surrounding amine and imidazolium groups. To gain a sample of optimal configurations to use, screening was completed on all possible rotations as has been completed on complex amine systems previously . Initially, this was completed on each epoxy monomer with the epoxy side chains rotated by 120° for sp 3 hybridized groups and 180° sp 2 groups.…”

“…To gain a sample of optimal configurations to use, screening was completed on all possible rotations as has been completed on complex amine systems previously. 43 Initially, this was completed on each epoxy monomer with the epoxy side chains rotated by 120°for sp 3 hybridized groups and 180°s p 2 groups. Following this analysis, all epoxy−IL cations within 10 kJ mol −1 were placed with an NTf 2 anion in five different configurations for each cation configuration.…”

“…The M06-2X DTF functional was used with Dunning’s cc-pVDZ basis set for optimization while for final energies the same DFT method was used with a cc-pVTZ basis set . These methods have been previously applied in similar IL-containing polymerization reaction system analysis as well as other reactions involving thermochemical prediction to obtain reliable geometries and energies which correlate to experiment. , A conductor-like polarizable continuum model (CPCM) using the dielectric constant of water was used to simulate the bulk solvent interactions with the specific polymerization environment . Water was chosen to emulate the highly polar local environment given by the surrounding amine and imidazolium groups.…”