A Computational Study of Lithium Enolate Mixed Aggregates

Abstract

Ab initio calculations were performed to examine the formation of mixed dimer and trimer aggregates between the lithium enolate of acetaldehyde (lithium vinyloxide, LiOV) and lithium chloride, lithium bromide, and lithium amides. Gas-phase calculations showed that in the absence of solvation effects, the mixed trimer 2LiOV.LiX is the most favored species. Solvation in ethereal solvents was modeled by a combination of specific coordination of dimethyl ether ligands on each lithium and "dielectric solvation" (DSE, dielectric solvation energies), immersion of each molecule in a cavity within a continuous dielectric having the dielectric constant of THF at room temperature. DSE is less important for aggregates (reduced dipoles or quadrupoles) than monomers (dipoles) and is also reduced for the coordinatively solvated species. Both solvation terms reduce the exothermicity of aggregation. In many cases, lithium salts that are three- rather than four-coordinate have significant populations at room temperature. The strongly basic lithium amides prefer mixed aggregates with weaker bases than homoaggregates. The computational results are consistent with the limited experimental data available.

Multi-level Modeling of Silica–Template Interactions During Initial Stages of Zeolite Synthesis

“…complex by 216 and 322 kJ/mol for water and ethanol, respectively. The solvation energy as shown in Table 2 originates from enclosing the complex in a cavity within a dielectric medium and is often referred to as the dielectric solvation energy (DSE) [72,87,88]. The DSE values are larger for ethanol than for water, in accordance with experimental observations by Kirschhock et al [41,43], stating that the precursor species are long-lived in ethanol, or at least more so than in water.…”

Insight into the Solvation and Isomerization of 3‐Halo‐1‐azaallylic Anions from Ab Initio Metadynamics Calculations and NMR Experiments

“…Theoretically the structures of a variety of organic lithium compounds were determined in the gas phase and in solvation using microsolvation with explicit ethereal ligands and/or continuum models. [31] For the 1-azaallylic anions as encountered here which are subject to large steric crowding, the degree of coordination is not a priori clear and can not be deduced straightforwardly from the experimental data. Isothermal-isobaric (NPT) molecular dynamics simulations during a period of 2.5 ps show that the Z-isomer 1 is monocoordinated whereas the E-isomer 2 features a two-fold coordination with THF (illustrated in Figure 3).…”

A Computational Study of Lithium Carbamate Synthetic Intermediate Structures and Aggregation

“…Since the concentration of pure THF or ether is different from the one M standard concentration c°, it was evaluated from its molar volume at 1 atm and 298.15 K using the empirical expression provided by Govender and coworkers [21] and incorporated into the second term of Equation (1). Numerically, this correction to ∆G° amounts to -1.4883 kcal/mol per THF and -1.3360 kcal/mol per diethyl ether at 298.15 K. This approach to modeling solvation effects on organolithium compounds has been used previously [22][23][24][25][26][27][28] and has been found to give results in good agreement with available experimental results.…”