Density Functional Theory with Implicit Solvents for Accurate Estimation of Aqueous and Organic Solvation Free Energies of Lignin Fragments

Abstract

Lignin is the main potential source of renewable aromatic chemicals, and solvation free energy (ΔG solv ) is a fundamental thermodynamic parameter for a compound in solution. Here, density functional theory with the electron density-based continuum solvent model (SMD-DFT) is employed to calculate ΔG solv for 283 neutral lignin depolymerization fragments and analogues (LDF&A) in water and organic solvents (1-octanol, cyclohexane, methyl-isobutyl ketone, and butyl acetate). Calculations for LDF&A are challenging due to the balance of hydrophilic oxygenations and hydrophobic aromatic rings with π orbitals. After correction of atomic van der Waals radii, calculated ΔG solv in water for a subset of 18 aromatic monomers is shown to outperform the accuracy of the FreeSolv benchmark. For organic solvents, comparisons through partition coefficients (log P) from several public datasets reveal that SMD-DFT calculations can accurately predict log P after accounting for systematic biases due to solvent admixtures not considered by the calculations. The presented results for LDF&A demonstrate that SMD-DFT provides useful estimates for log P and unprecedented accuracy for aqueous ΔG solv . The obtained datasets of aqueous and organic ΔG solv for LDF&A provide a key advancement toward accurate computer modeling of lignin processing into renewable fuels and chemicals.

“Domino” synthesis of bio-derived anethole over facile-prepared hafnium phosphonate frameworks with efficient bifunctional acid sites

“…Considering that the catalytic reaction was carried out in a solvent system, the solvation effect was incorporated into the geometric optimization via the SMD model. 34…”

Effect of Solvent on the Interaction of Lignin with a Zeolite Nanosheet in the Condensed Phase

“…In this regard, computational methods such as quantum mechanical calculation, molecular dynamics, and Monte Carlo simulation can provide a detailed understanding of the solvation nature, lignin–solvent interactions, lignin–catalyst interaction, site-specific catalytic activity, structure in the condensed phase, etc. Density functional theory methods are used to understand activation/bond dissociation energy, − solvation, − and catalyst–lignin interaction. , Due to high computational cost, DFT calculations are often limited to mono/dimer of lignin in the gas phase. Classical molecular dynamics simulation is rigorously used to understand the condensed phase solvation and conformation of lignin. − Even though lignin depolymerization on zeolite-based catalyst holds a significant promise, theoretical studies of condensed phase, large scale, and long-chain lignin are still unexplored.…”