Density Functional Theory/GIAO Studies of the ~13C, ~15N, and ~1H NMR Chemical Shifts in Aminopyrimidines and Aminobenzenes: Relationships to Electron Densities and Amine Group Orientations

摘要

The dependence of the ~13C, ~15N, and ~1H isotropic NMR chemical shifts on amine substitution of aromatic ring systems are examined both experimentally and by DFT/GIAO(density functional theory/gauge including atomic orbitals) methods. These are large, monotonic decreases in the chemical shifts at odd-numbered (ortho and para) pyrimdine ring positions which do not occur at the even-numbered (ipso and meta) atoms as amine groups progressively replace hydrogens at the latter positions.