New torsion potential expression for molecules without rotational symmetry

Area of Science:

• Computational Chemistry
• Molecular Modeling
• Quantum Chemistry

Background:

• Accurately describing bond rotations is crucial for molecular modeling.
• Existing torsion potential functions, like truncated Fourier series, can be complex to interpret and parameterize.
• Functions without rotational symmetry require specialized approaches.

Purpose of the Study:

• To propose a new, intuitive torsion potential function for bond rotations lacking rotational symmetry.
• To develop a function that easily determines the number of terms needed for barrier representation.
• To provide a clear physical interpretation of the function's expansion parameters.

Main Methods:

• Developing a torsion potential function based on Gaussian-type terms.
• Each term represents an eclipsed conformation of 1,2-substituents on C-C bonds.
• Applying the function to model 1,2-substituted haloethanes.

Main Results:

• The proposed Gaussian-type function offers a straightforward way to determine the required number of terms for torsion potential barriers.
• Expansion parameters intuitively correspond to barrier height, dihedral angles of eclipsed conformations, and substituent size.
• Successful application to 1,2-substituted haloethanes, requiring three Gaussian terms for fully and partially eclipsed conformations.

Conclusions:

• The new Gaussian-type torsion potential function provides an interpretable and efficient alternative for modeling complex bond rotations.
• This method simplifies the analysis of conformational preferences and energy barriers in molecules.
• The function's intuitive parameterization aids in understanding substituent effects on molecular conformations.