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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