Solvatochromic Measurement of KAT Parameters and Modeling Preferential Solvation in Green Potential Binary Mixtures of N-Formylmorpholine with Water, Alcohols, and Ethyl Acetate

Abstract

Kamlet−Abboud−Taft (KAT) solvatochromic parameters (α, β, and π*), as well as the Reichardt's polarity scale (E T (30)), were measured from ultraviolet−visible (UV−vis) absorption spectral shift of three indicator solutes namely 4nitroaniline, N,N-dimethyl-p-nitroaniline, and the betaine dye 4-(2,4,6-triphenylpyridinium-1-yl)-2,6-diphenylphenolate. These measurements were done within the whole mole fraction range of the binary mixture of green solvents N-formylmorpholine with water, ethanol, 1-propanol, 2-propanol, 1-butanol, and ethyl acetate at room temperature (298.15 ± 0.1 K). The Redlich−Kister model was employed to demonstrate the effect of solvent composition on the solvatochromic parameters obtained in the mixtures understudy. The data of E T obtained for the indicator dyes in different mole fractions (0.0−1.0) of the binary mixtures were analyzed to investigate their preferential solvation in terms of both the solute−solvent and the solvent−solvent interactions. The solvent exchange model was successfully utilized to calculate preferential solvation parameters. It was found that the solvation shell of the dyes is mainly affected by the solvent−solvent interactions, and all studied systems showed the nonideal behavior.

Assessing the Temperature-Dependent Tunable Polarity of N,N-Dimethylcyclohexylamine (DMCHA) and Water Mixtures

“…Measured wavenumbers for both NND4 and 4NAi are shown to be in good agreement with the literature for all reference solvents (Table 1). 14,26,27 The π* values for all solvents are constant or slightly decrease as temperatures increases (Figure 1a). Since the π* trend for dry DMCHA is comparable to that of the reference solvents, temperature does not seem to uniquely impact the π* of dry DMCHA.…”

“…This change in the temperature responsiveness of wet DMCHA is evidence of a synergistic interaction between DMCHA and water. 14 Interaction between the system components can be further analyzed using the wavenumber (maximum frequency) of the π* dye, NND4, with wet DMCHA. If there was no interaction between the water and DMCHA, then the wavenumber would be a simple weighted average of the wavenumbers for each pure component (DMCHA and water).…”

“…However, in a homogeneous solvent mixture, the probe molecule can interact differently toward one species over the other. 14,32 This is caused by solvent−solute and solvent− solvent intermolecular interactions in the solution system. 14 If preferential solvation is occurring, the question becomes: is the measured parameter representative of the bulk solution or only of a solvation shell around the probe?…”

“…Individual stock solutions of 4-nitroaniline (4NAi), N,N-dimethyl-4-nitroaniline (NND4), 4-nitroanisole (4NA), and Reichardt's dye (RD) were prepared in acetone. 14 Binary solutions of water in DMCHA were prepared on a mass basis and were carried out under the hood with an uncertainty of ±0.1 mg. 14 All solvents and binary solutions were stored in screw cap amber glass vials and were kept in a dry wellventilated environment. 15 To prepare the working dye/solvent solution, the dye−acetone stock solution was micropipetted into a clean, dry 4 mL glass vial.…”

“…14 3 mL of the appropriate solvent/ binary solution was then added to the glass vial with the probe and vortexed for 45 s. A clean dry Teflon stirring flea was added to a 10 mm path length quartz screw cap cuvette. 14 2 mL of the appropriate working solution was then added to the quartz cuvette and capped immediately. 15 The dye concentrations were adjusted to maintain the maximum absorbance below 1 absorbance unit.…”