Solvation of o-hydroxybenzoic acid in pure and modified supercritical carbon dioxide, according to numerical modeling data

Abstract

The dissolution of an elementary fragment of crystal structure (an o-hydroxybenzoic acid (o-HBA) dimer) in both pure and modified supercritical (SC) carbon dioxide by adding methanol (molar fraction, 0.035) at T = 318 K, ρ = 0.7 g/cm 3 is simulated. Features of the solvation mechanism in each solvent are revealed. The solvation of o-HBA in pure SC CO 2 is shown to occur via electron donor-acceptor interactions. o-HBA forms a solvate complex in modified SC CO 2 through hydrogen bonds between the carboxyl group and methanol. The hydroxyl group of o-HBA participates in the formation of an intramolecular hydrogen bond, and not in interactions with the solvent. It is concluded that the o-HBA-methanol complex is a stable molecular structure, and its lifetime is one order of magnitude higher than those of other hydrogen bonds in fluids.

Solvation of salicylic acid in pure, methanol-modified and water-modified supercritical carbon dioxide: Molecular dynamics simulation

“…Formation of solvated shells of salicylic acid is likely to take place within given time frames. In pure sc-CO 2 this process is governed by weak HBs and electron donor-accepter interactions with CO 2 [41]. In modified sc-CO 2 solvation of salicylic acid proceeds via formation of strong HBs with co-solvent.…”