Measuring molecular parity nonconservation using nuclear magnetic resonance spectroscopy

TL;DR

This paper proposes a novel NMR spectroscopy method to detect molecular parity nonconservation by measuring diastereomeric splittings as a function of enantiomeric excess, setting new experimental constraints on PNC effects.

Contribution

It introduces a new NMR-based experimental approach to measure molecular PNC effects and provides the first constraint on PNC in extsuperscript{13}C chemical shifts.

Findings

Set a new constraint on molecular PNC at 10^{-5} ppm in extsuperscript{13}C resonances.

Demonstrated proof-of-principle experiment using extsuperscript{13}C and extsuperscript{1}H NMR.

Discussed key considerations for future molecular PNC detection using NMR.

Abstract

The weak interaction does not conserve parity and therefore induces energy shifts in chiral enantiomers that should in principle be detectable in molecular spectra. Unfortunately, the magnitude of the expected shifts are small and in spectra of a mixture of enantiomers, the energy shifts are not resolvable. We propose a nuclear magnetic resonance (NMR) experiment in which we titrate the chirality (enantiomeric excess) of a solvent and measure the diasteriomeric splitting in the spectra of a chiral solute in order to search for an anomalous offset due to parity nonconservation (PNC). We present a proof-of-principle experiment in which we search for PNC in the \textsuperscript{13}C resonances of small molecules, and use the \textsuperscript{1}H resonances, which are insensitive to PNC, as an internal reference. We set a new constraint on molecular PNC in \textsuperscript{13}C chemical shifts at a level of $10^{-5}$\,ppm, and provide a discussion of important considerations in the search for molecular PNC using NMR spectroscopy.