13C-NMR CHEMICAL SHIFTS OF DIFLUOROMETHYLENE GROUPS

Substituent Effects on 13c Nmr Chemical Shifts in Dialkylaminophenylchlorophosphines

The relative chemical shifts and 2J(PC) coupling constants in the low-temperature limiting spectra of a series of Ph(R,N)PCl compounds [R = Me, Et, PhCH2, ‘Pr and c-Hex] differ for R = primary or secondary. For primary alkyl substituents, the more downfield signal exhibits a large, positive coupling and the more upfield resonance shows a small, negative coupling. These observations are reversed...

Computed 13C NMR Chemical Shifts via Empirically Scaled GIAO Shieldings and Molecular Mechanics Geometries. Conformation and Configuration from 13C Shifts

Accurate (rms error ∼3 ppm) predictions of 13C chemical shifts are achieved for many of the common structural types of organic molecules through empirical scaling of shieldings calculated from gauge including atomic orbitals (GIAO) theory with a small basis set and with geometries obtained from computationally inexpensive molecular mechanics methods. Earlier GIAO calculations are shown to be mu...

Dependence of 13C NMR chemical shifts on conformations of rna nucleosides and nucleotides.

Cross-polarization magic-angle spinning solid-state NMR spectroscopy has been used to investigate the dependence of (13)C sugar chemical shifts on specific conformational parameters of a variety of ribonucleotides and ribonucleosides. Solid-state NMR is a valuable tool for nucleoside and nucleotide structural studies since it provides the means to acquire spectra that correspond to single confo...

A New Development of Electronic Descriptors for Simulation of 13C Chemical Shifts

The 13C chemical shifts for a series of compounds which includes carboxylic acids, aldehydes, ethers, ketones and hydrocarbons were simulated by using the parametric techniques. The observed chemical shifts were related to numerically encoded structural parametes called descriptors. Two new electronic descriptors were added to the previous descriptors. Ploting of experimental ver...

H Chemical Shifts in NMR