摘要:
Enantomer discrimination is revealed in the H-1-NMR spectra of partially resolved samples of seven chiral carboxamides. Signal separation is temperature and concentration dependent, and it varies smoothly with enantiomer composition, being a maximum when the difference in enantiomer content is also a maximum and coalescing to one signal in racemic material. These effects are interpreted in terms of linear hydrogen-bonded arrays of amide molecules, which undergo exchanges of the end units at rates that give rise to two different averaged environments when the enantiomer composition is different.