Subtle Effects of Aliphatic Alcohol Structure on Water Extraction and Solute Aggregation in Biphasic Water/n-Dodecane

Area of Science:

• Physical Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Understanding organic phase behavior is crucial for chemical separations and formulations.
• Alcohols can form aggregates in nonpolar solvents, influencing macroscopic properties.
• The role of alcohol structure in aggregation within biphasic systems requires detailed investigation.

Purpose of the Study:

• To investigate the organic phase aggregation behavior of 1-octanol and 2-ethylhexanol.
• To elucidate the influence of alcohol structure on water uptake and aggregate formation.
• To correlate molecular interactions with macroscopic physical properties.

Main Methods:

• Combined use of physical measurements, small-angle X-ray scattering (SAXS), and atomistic molecular dynamics simulations.
• Quantification of water uptake using Karl Fischer titrations.
• Assessment of water extraction via the slope-analysis method.

Main Results:

• Interfacial tension decreased with increasing alcohol concentration, with no critical aggregate concentration observed.
• Significant water uptake into the organic phase was quantified and correlated with alcohol content.
• SAXS data revealed aggregate formation in n-dodecane at higher alcohol concentrations, dependent on alcohol tail group geometry.

Conclusions:

• Alcohol structure dictates aggregate morphology and water solubilization in biphasic systems.
• Hydrogen bonding between alcohol-alcohol and alcohol-water molecules drives aggregate formation.
• Findings provide molecular-level insights into the behavior of amphiphilic molecules in nonpolar media.