Anomalous Viscosity of a Racemate: A Simple Experiment Demonstrating Chirally Induced Spin Selectivity

Area of Science:

• Physical Chemistry
• Chemical Physics
• Molecular Dynamics

Background:

• Racemic solutions of hydrogen-bonded compounds exhibit lower viscosity than their constituent enantiomers, a long-standing observation.
• This phenomenon has remained scientifically unexplained for over a century.

Purpose of the Study:

• To investigate the anomalous viscosity of racemic solutions compared to enantiomers.
• To explore the underlying molecular mechanisms responsible for this viscosity difference.
• To test the applicability of classical molecular dynamics simulations in explaining the phenomenon.

Main Methods:

• Experimental confirmation using lactic acid enantiomers and their racemic mixture.
• Molecular dynamics (MD) simulations of lactic acid viscosity.
• Comparison of experimental results with classical MD simulation outcomes.

Main Results:

• Experimental data confirmed that racemic lactic acid solutions are less viscous than their enantiomers.
• Classical molecular dynamics simulations failed to reproduce the observed anomalous viscosity.
• The study highlights the limitations of classical MD in capturing this specific molecular behavior.

Conclusions:

• The anomalous viscosity of racemates is not explained by classical molecular dynamics.
• A recently discovered magnetic intermolecular force, arising from spin-dependent charge reorganization, is proposed as a potential explanation.
• This finding opens new avenues for understanding intermolecular forces and solution properties.