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13 C NMR spectra of polyalkoxymethanes, and their sulphur‐ and nitrogen‐containing analogues, of an aliphatic series. Inclusion of non‐bonded interactions by the use of CO bond increments
Author(s) -
Dostovalova V. I.,
Zlotsky S. S.,
Rakhmankulov D. L.,
Terent'ev A. B.
Publication year - 1987
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260250102
Subject(s) - geminal , chemistry , heteroatom , chemical shift , isostructural , sulfur , nitrogen , nmr spectra database , carbon 13 nmr , computational chemistry , nuclear magnetic resonance spectroscopy , crystallography , stereochemistry , spectral line , organic chemistry , ring (chemistry) , crystal structure , physics , astronomy
13 C NMR spectra of 40 substituted acetals, carbonates, ortho ethers, 1,3‐dioxocycloalkanes, 1,3‐oxothiolanes and 1,3‐oxazolidines were studied. The chemical shift of the C‐α carbon atom was found to depend both on the number ( K ) and type of the hetero substituents at C‐α. The effect of oxygen, nitrogen and sulphur atoms on the C‐α chemical shift was shown to be a non‐additive property relative to the unsubstituted isostructural hydrocarbons. The C‐α chemical shift in the linear and cyclic polyalkoxymethanes can be described by an equation incorporating CO bond increments and contributions from the RO substituents:\documentclass{article}\pagestyle{empty}\begin{document}$$ \delta \left({^{13} {\rm C} - \alpha } \right) = \delta \left({^{13} {\rm CH}_4 } \right) + K\Delta \delta \left({{\rm C} - {\rm O}} \right) + \sum _k \Delta {\rm RO} $$\end{document}The CO increment depends quadratically on the number ( K –1) of geminal neighbours of the oxygen atom under study. Good agreement between the experimental and calculated shifts can only be achieved by inclusion of nonbonded interactions between the geminal heteroatoms.