Abstract13C 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 CO 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 CO 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 betwee