Trends in shift rules in carbon-13 nuclear magnetic resonance spectroscopy and computer-aided shift prediction

H NMR Analysis of Chain Unsaturations in Ethene/1-Octene Copolymers Prepared with Metallocene Catalysts at High Temperature

“…We ascribe the unusually high-field value of 1 H chemical shift of Vy3 -a to a rigid conformation imposed by the two sterically demanding alkyl substituents, forcing the proton in question out of the deshielding cone of the double bond. The assignment is consistent with a calculated 13 C chemical shift value for Vy3 -a of 42.4 ppm (according to the CSPEC method), and also with the results of the 1 H{ 1 H} experiment; in fact, selective irradiation of the allylic protons in the 2.03−1.90 ppm range (including the Vy3 -d protons) changed the double triplet of Vy3 -c at 5.30 ppm into a doublet ( J = 15.5 Hz), due to residual coupling with Vy3 -b. The multiplet at 5.11 ppm, on the other hand, was unaffected, because proton Vy3 -a at 1.86 ppm was not irradiated.…”

C13Shift: a computer program for the prediction of carbon-13 NMR spectra based on an open set of additivity rules

“…For a 2,5-disubstituted indole, the increments of the 2-substituent X for pyrrole (fourth line in Figure 3) will be used to estimate the shifts of the atoms 1-3,8, and 9 and the increments for benzene will replace the increments of the 6-substituent Y for the atoms 6-9 if these substituents are missing in the indole substituent file. The contributions of X to the shifts [4][5][6][7] and those of Y to 2-3 will be neglected.…”

Synthesis of an Amine−Oleate Derivative Using an Ionic Liquid Catalyst

“…In the 13 C NMR, the assignments reasonably follow the empirical shift rules (33). It is of interest that at 125 MHz, the two products A and B give distinctly different peaks for all carbons, except for C-18, and carbons from aniline, methoxy, and ester.…”

“…Despite the large number of distinctive carbons and proton present, we are able to achieve almost complete assignments through a combination of empirical shift rules (33), chemical shifts of analogous compounds (34)(35)(36), and two-dimensional NMR. For future reference, the 1 H-13 C HSQC plot is given in Figure 3.…”