Henry’s Law Constants for Fragrance and Organic Solvent Compounds in Aqueous Industrial Surfactants

Abstract

Henry’s law constants (kH) were measured (at 30 °C) and modeled for a suite of fragrance and solvent compounds in aqueous solutions of three structurally diverse industrial surfactants: sodium dodecylbenzene sulfonate (NaDBS), tetradecylbenzyldimethyl ammonium chloride (TDBAC), and a linear alkyl ethoxylate, Neodol 1,9. kH values for limonene, β-pinene, toluene, and trichloroethene were examined as a function of surfactant concentration. When compared to TCE and toluene, the fragrances limonene and β-pinene with their larger values of molecular polarizability (ὰmol = (17.94 ± 0.5) Å3and (17.34 ± 0.5) Å3, respectively) and greater hydrophobic character exhibited greater affinity for micelles of the linear alkyl ethoxylate relative to those of NaDBS and TDBAC and greater selectivity overall in their interaction(s) with micelles of varying carbon content (Cn). Using a linear solvation energy relationship (LSER) of the form ln kH = C + sπ2* + aΣα2 + bΣβ2 (π2* = solute dipolarity/polarizability; Σα2 = overall solute hydrogen-bond-donor acidity; Σβ2 = overall solute hydrogen-bond-acceptor basicity; C = a regression constant) as an additional correlation and characterization tool, we find the large negative coefficients on π2*, Σα2, and Σβ2 consistent with the inverse correlation between ln kH and the magnitude of solute–solvent interactions in the condensed phase; C decreases with increasing size of the micellar phase. The dominance of HBD and HBA interactions (Σα2 and Σβ2, respectively) in the LSER for the alkyl ethoxylate points to the role of the ethylene oxide outer portion of the Neodol 1,9 micelles along with the effect of intercalated water.