Measuring molecular parity nonconservation using nuclear-magnetic-resonance spectroscopy

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 C-13 resonances of small molecules, and use the H-1 resonances, which are insensitive to PNC, as an internal reference. We set a constraint on molecular PNC in C-13 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.