An alternative interpretation of the HETCOR NMR spectra of poly(lactide)

Abstract

An alternative to the assignments proposed recently by Chisholm et al. for the ¹H and ¹³C NMR resonances of poly(lactide) based on their HETCOR spectra is presented; we find that the HETCOR spectra are consistent with older assignments of the tetrad and hexad stereosequence resonances in the ¹H and ¹³C NMR spectra and we believe that the influence of adjacent chiral units on the NMR chemical shift extends asymmetrically and is opposite in the case of ¹H and ¹³C nuclei; this is in contrast to the assumption that the observed chiral repeat unit for any particular stereosequence resonance is the same for ¹H and ¹³C NMR spectra as used by Chisholm et al. in their analysis.

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