Self-Associating Behavior of Acetone in Liquid Krypton

Area of Science:

• Physical Chemistry
• Spectroscopy
• Computational Chemistry

Background:

• Acetone's large dipole moment drives self-association through dipole-dipole interactions.
• Investigating molecular self-association requires advanced spectroscopic and computational techniques.
• Previous studies have limited spectral data on acetone dimers.

Purpose of the Study:

• To investigate acetone self-association in liquid krypton using infrared spectroscopy.
• To determine the thermodynamical properties of acetone dimerization.
• To elucidate the geometrical structures of acetone dimers through theoretical calculations.

Main Methods:

• Infrared spectroscopy of acetone in liquid krypton at various concentrations and temperatures.
• Numerical analysis using least-squares fitting to resolve overlapping monomer and dimer spectra.
• High-level ab initio calculations (MP2/aug-cc-pVDZ, CCSD(T)) to determine dimer geometries and energies.

Main Results:

• Isolated acetone dimer absorption bands were observed across the mid-infrared spectrum.
• Experimental standard dimerization enthalpy determined to be -10.8 kJ mol⁻¹.
• Calculations predicted a more stable stacked dimer geometry compared to a planar one, with complexation energies of -28.4 kJ mol⁻¹ (stacked) and -15.1 kJ mol⁻¹ (planar).
• Solution complexation enthalpies were calculated as -13.7 kJ mol⁻¹ (stacked) and -5.8 kJ mol⁻¹ (planar).

Conclusions:

• Advanced numerical methods successfully resolved complex infrared spectra of acetone dimers.
• The study provides detailed thermodynamic and structural insights into acetone self-association.
• The findings contribute to understanding intermolecular forces and molecular aggregation in condensed phases.