The effect of electron-withdrawing groups on¹⁵N and¹³C chemical shifts: a density functional study on a series of pyrroles

15N and 13C NMR chemical shifts of 6‐(fluoro, chloro, bromo, and iodo)purine 2′‐deoxynucleosides: measurements and calculations

“…Figure 7 shows a plot of measured and calculated coupling constants with both basis sets. In general, reasonable agreement is found between the calculated and experimental 19 F-15 N and 19 F-13 C coupling constants for both basis sets. However, the DFT calculations with the bigger Figure 6.…”

“…2) along the 15 N dimension is due to the long-range coupling of 19 F and 15 N, with J F−N1 = 47 Hz. [3] From Fig.…”

“…For example, DFT calculations of pyrroles show that differences in the 15 N chemical shifts are almost exclusively the result of changes in the paramagnetic contribution due to the substituent. [19] In addition, calculated chemical shifts have been shown to be quite sensitive to molecular conformation. [20,21] We have carried out calculations of the 15 N and 13 C chemical shifts of the four 6-halopurine 2-deoxynucleoside derivatives with the Gaussian03 program package.…”

The Use of NMR Chemical Shifts to Predict Reaction Pathways: Methanol Formation from Oxazolidinones

“…Again, 13 C and 15 N chemical shifts correlate with different signs. In this plot a principle trend can be observed, and it should be possible to predict the reaction pathway by means of the σ p value, although the theoretical understanding of 15 N chemical shifts is complex 12. Notable to mention is the fact, that the CF 3 SO 2 group has the highest σ p value as well as the highest group electronegativity of all substituents compared in this paper.…”

Experimental and theoretical characterization of a novel bis‐pyrazoylmethane ligand

“…). Under these conditions, the proton‐17 experiences the strong anisotropic deshielding effect of the two pyrazole rings, fundamentally.…”