Proximity effects on the nuclear magnetic shielding tensor. Part 1. An ab initio study of 17O and 19F chemical shifts in the proximity of a methyl group

The deshielding effect produced by repulsive interactions between proximate groups was studied from a theoretical point of view, calculating the magnetic shielding constants for the following nuclei: ¹⁷O in di-coordinated and carbonyl oxygen atoms; ¹⁹F and ¹³C. The "super molecule" approach was used to study the proximity effect in the following three model systems: water-methane; formaldehyde-methane; methyl fluoride-methane, calculating the chemical shieldings for various intermolecular distances. Calculations were carried out using the giao approach with an ab initio ground state wavefunction calculated with the 6-31G^** basis set. Linear correlations are found between the intermolecular effects on the magnetic shielding constants and the interaction energies, yielding an increase in the deshielding effect when increasing the repulsion between the two molecules. © 1993.

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Author Julio Cesar Facelli Biostatistics & Bioinformatics, Division of Translational Bi ...