The structure of liquid methanol.

Area of Science:

• Computational chemistry
• Physical chemistry
• Molecular modeling

Background:

• Understanding the structure of liquids is crucial for predicting their properties.
• Previous models of liquid methanol often assumed linear or open-chain structures.
• Experimental data for liquid methanol's thermodynamic and spectroscopic properties are well-established.

Purpose of the Study:

• To determine the dominant molecular structures in liquid methanol.
• To reconcile theoretical calculations with experimental observations.
• To investigate the role of cyclic and open-chain structures in liquid methanol.

Main Methods:

• Density functional calculations were performed on molecular clusters.
• A quantum cluster equilibrium (QCE) model was employed.
• Theoretical results were compared with experimental thermodynamic and spectroscopic data.

Main Results:

• Liquid methanol is predominantly composed of cyclic and/or lasso structures.
• Models including these cyclic structures accurately reproduced experimental heat of vaporization, heat capacity, NMR chemical shifts, and quadrupole coupling constants.
• Models based on open-chain structures failed to match experimental values.

Conclusions:

• Cyclic and lasso structures are key to understanding liquid methanol's behavior.
• The QCE model combined with DFT calculations provides a robust method for studying liquid structures.
• Open-chain structures alone cannot explain the observed properties of liquid methanol.