Antisymmetric Couplings Enable Direct Observation of Chirality in Nuclear Magnetic Resonance Spectroscopy

TL;DR

This paper demonstrates that antisymmetric J-coupling in nuclear magnetic resonance directly relates to molecular chirality, enabling enantiomer differentiation without chiral agents through an NMR experiment sensitive to molecular orientation.

Contribution

The study introduces a novel NMR method to observe antisymmetric J-coupling linked to chirality, providing a new way to distinguish enantiomers without added chiral substances.

Findings

Antisymmetric J-coupling is connected to molecular chirality.

The proposed NMR experiment can differentiate enantiomers.

Sign change in coupling affects NMR spectrum phase.

Abstract

Here we demonstrate that a term in the nuclear spin Hamiltonian, the antisymmetric \textit{J}-coupling, is fundamentally connected to molecular chirality. We propose and simulate a nuclear magnetic resonance (NMR) experiment to observe this interaction and differentiate between enantiomers without adding any additional chiral agent to the sample. The antisymmetric \textit{J}-coupling may be observed in the presence of molecular orientation by an external electric field. The opposite parity of the antisymmetric coupling tensor and the molecular electric dipole moment yields a sign change of the observed coupling between enantiomers. We show how this sign change influences the phase of the NMR spectrum and may be used to discriminate between enantiomers.