Mechanism of Hydrotropic Action of Hydrotrope Sodium Cumene Sulfonate on the Solubility of Di-t-Butyl-Methane: A Molecular Dynamics Simulation Study

Abstract

Hydrotropes are special class of amphiphilic molecules that have an ability to solubilize the insoluble or sparingly soluble molecules in water. To find out the mechanism of hydrotropic action of hydrotropes on hydrophobic molecules, we have carried out classical molecular dynamics simulation of hydrophobic solute di-t-butyl-methane (DTBM) and hydrotrope sodium cumene sulfonate (SCS) in water with a regime of SCS concentrations. Our study demonstrates that, above the minimum hydrotrope concentration (MHC), the self-aggregation of SCS starts, and it creates a micellar-like environment in which the hydrophobic tail part of SCS points inward while its hydrophilic sulfonate group points outward to make favorable contact with water molecules. The formation of the hydrophobic core of SCS cluster creates a hydrophobic environment where the hydrophobic DTBM molecules are encapsulated. Interestingly, the determination of average water-SCS hydrogen bonds further suggests that the aggregate formation of SCS molecules has a negligible influence on it. Moreover, the calculations of Flory-Huggins interaction parameters also reveal favorable interactions between hydrotrope SCS and solute DTBM molecules. The implications of these findings on the mechanism of hydrotrope assisted enhanced solubility of hydrophobic molecules are discussed.

Rapid and near-complete dissolution of wood lignin at ≤80°C by a recyclable acid hydrotrope

“…Most hydrotropes aggregate above MHC ( 18 , 19 ), or critical aggregate concentration, to solubilize hydrophobic materials. We determined the MHC of p -TsOH from the conductivities of its solutions ( 20 ).…”

“…Because of variations in hydrotrope structures, the exact mechanism of a given hydrotrope solubilizing compounds is still under debate ( 18 ). However, most researchers believe that most hydrotropes aggregate above the MHC ( 18 , 19 ). Aggregation is pronounced in the presence of a hydrophobic solute ( 34 ).…”

“…We further hypothesize that the lipophilic nonpolar part (toluene moiety) of the p -TsOH molecule can shield the separated lignin through the π-π stacking or hydrophobic interaction to form micellar-like aggregates to prevent the reaggregation of lignin, whereas the hydrophilic end (sulfonic acid moiety) points outward to water for effective dissolution ( Fig. 1B ) ( 19 ).…”

Acid Hydrotropic Fractionation of Lignocelluloses for Sustainable Biorefinery: Advantages, Opportunities, and Research Needs

“…Hydrotropic phenomenon was discovered in 1916 by Neuberg [52] . It refers to solubilization of hydrophobic materials in aqueous systems by hydrotrope aggregation around the solute [53–55] . Current applications are mainly in the pharmaceutical industry [56] .…”

Exploring the binding sites and binding mechanism for hydrotrope encapsulated griseofulvin drug on γ-tubulin protein

“…They can self-aggregate in aqueous solution above minimum hydrotrope concentration (MHC) [ 37 ]. Most interestingly hydrotropes have an ability to solubilize the insoluble or sparingly soluble molecules in water [ 38 , 39 ]. In our previous study we have shown the mechanism of hydrotropic action by formulating griseofulvin with hydrotrope sodium cumene sulfonate (SCS) molecules (See Fig 1 (c) ) [ 39 ].…”