Separation of Enantiomers through Local Vorticity: A Screw Model Mechanism

Area of Science:

• Chemical Physics
• Fluid Dynamics
• Molecular Dynamics

Background:

• Enantiomeric separation is crucial in pharmaceuticals and chemistry.
• Existing separation methods often face challenges in efficiency and scalability.
• Understanding the fundamental mechanisms of chiral molecule behavior in fluids is essential.

Purpose of the Study:

• To present a novel model explaining enantiomeric separation driven by fluid flow.
• To introduce and utilize the concept of "molecular pitch" to quantify chiral separation.
• To demonstrate the potential for efficient, large-scale enantiomeric separation using fluid dynamics.

Main Methods:

• Developed a theoretical model coupling molecular rotation and translation in fluids.
• Introduced and computed "molecular pitch" using hydrodynamic resistance tensors.
• Performed simulations of model enantiomers (e.g., [Ru(bpy)3]Cl2, atorvastatin) in various solvents.
• Utilized competition models and drift-diffusion equations for racemic mixture separation.

Main Results:

• Local fluid vorticity induces molecular rotation, coupling with translation to drive enantiomers apart.
• Molecular pitch effectively predicts the degree of translation-rotation coupling.
• Simulations and experimental data support the model's predictions for chiral separation.
• Achieved centimeter-scale enantiomeric separation within hours using achievable vorticities.
• Identified that some achiral molecules can also exhibit a non-zero molecular pitch.

Conclusions:

• The presented model provides a mechanistic understanding of enantiomeric separation in fluid flow.
• Molecular pitch is a valuable, computable metric for predicting chiral separation efficiency.
• Fluid-driven enantiomeric separation offers a promising route for scalable and efficient chiral resolution.