A computational study of conformational interconversions in 1,4-dithiacyclohexane (1,4-dithiane)

Area of Science:

• Computational Chemistry
• Organic Chemistry
• Molecular Modeling

Background:

• 1,4-dithiacyclohexane (1,4-dithiane) is a six-membered heterocyclic compound.
• Understanding its conformational preferences is key to predicting its chemical properties and reactivity.

Purpose of the Study:

• To computationally investigate the conformational interconversions of 1,4-dithiane.
• To determine the relative energies, enthalpies, entropies, and free energies of its chair and twist conformers.
• To locate and characterize transition states involved in these conformational changes.

Main Methods:

• Ab initio molecular orbital theory using various basis sets (e.g., 6-31G(d), 6-311+G(2d,p)).
• Density functional theory (DFT) with functionals like BLYP and B3LYP.
• Intrinsic Reaction Coordinate (IRC) calculations to verify transition state pathways.

Main Results:

• The 1,4-boat transition state is significantly higher in energy than chair and 1,4-twist conformers.
• The chair conformer is more stable than the 1,4-twist conformer, with a free energy difference (ΔG°(c-t)) of 4.93 kcal/mol at 298.15 K.
• IRC calculations confirmed transition states for chair-twist and twist-enantiomer interconversions.

Conclusions:

• The study provides detailed energetic profiles for 1,4-dithiane conformational changes.
• Absence of significant hyperconjugative interactions was noted in chair and 1,4-twist conformers.
• The computational methods employed offer insights into the conformational landscape of similar heterocyclic systems.