NMR 13C spectra

Peculiarities of 13C NMR spectra of benzoyl fragment of benzoylformic acid and its esters have been investigated and characteristic values of a chemical shift of all five types of fragment atom have been examined. Similar parameters of other benzoyl-containing compounds by general formula Bz–X (X = H, NR2, OR, SR, Cl, Br), as well as those of compounds Bz–C (L)(M)(N) have been compared. It has been shown that spectral peculiarities of a benzoylformates phenyl fragment are defined by the carbonyl, not by the carbalkoxyl group.

It has been shown that chemical shift of 5 types of carbon nuclei of benzoyl fragment in saturated alkylbenzoates depends upon alkyl radical degree of branching near α-carbon atom of alkoxyl group. Typical values of chemical shifts of five nuclei for primary, secondary and tertiary alkylbenzoates have been admitted

Differential spectral parameters δС of some primary, secondary, and tertiary alkylbenzoates have been calculated. Such parameters are the differences between the two basic spectral parameters – δС values in NMR 13C spectra. The effective usage of differential spectral parameters has been shown using particular spectral task for primary alkylbenzoates as an example.

Application of increments additivity allows to attribute closed by value signals in the area of 28 ppm in NMR 13C spectra of 1-pentanol (I) and its esters (II, III) for C2 and C3 atoms during calculations of δС2 and δС3 chemical shifts. In case of pentylformate (IIa) on the basis of calculated data it has been suggested to interchange attributions made by authors [2].