Liquid structure of dibutyl sulfoxide

Area of Science:

• Physical Chemistry
• Materials Science
• Chemical Physics

Background:

• Understanding the structure of liquid organic compounds is crucial for predicting their properties.
• Dibutyl sulfoxide (DBSO) possesses both polar (sulfoxide group) and apolar (butyl chains) characteristics, suggesting complex structural behavior.

Purpose of the Study:

• To experimentally determine the structure of liquid dibutyl sulfoxide (DBSO) at 320 K.
• To rationalize the experimental data using molecular dynamics (MD) simulations.
• To investigate the nature and extent of structural differentiation and intermolecular interactions in DBSO.

Main Methods:

• X-ray diffraction experiments were conducted on liquid DBSO at 320 K.
• Molecular dynamics (MD) simulations were employed to model and interpret the structural data.
• Analysis of diffraction patterns, specifically the low Q peak, and simulation trajectories.

Main Results:

• X-ray diffraction data revealed a distinct structural differentiation at the nanometer scale, indicated by a low Q peak.
• MD simulations confirmed enhanced dipole-dipole correlations in DBSO compared to shorter-chain analogs like DMSO.
• A moderate Kirkwood correlation factor and self-association were observed, attributed to these dipole-dipole interactions.
• Hydrogen bonding between oxygen and butyl chain hydrogens was found to be limited, with only α-hydrogens showing a slight indication of interaction, as a consequence of dipole-dipole correlation.

Conclusions:

• Dibutyl sulfoxide exhibits significant polar-apolar structural segregation due to its molecular architecture.
• Strong dipole-dipole correlations are the dominant intermolecular force, driving self-association.
• The role of hydrogen bonding in DBSO's structure is less significant than previously assumed and is largely a consequence of dipole-dipole effects.