Primary 1 H/ 2 H isotope effect in the NMR chemical shift of HClO 4 salts of 1,8‐bis(dimethylamino)naphthalene derivatives

The primary 1 H/ 2 H isotope effect for a number of protonated naphthalene proton sponges (DMAN‐s) was measured and correlated with the δ ( 1 H) value and IR spectroscopic characteristics of the [NHN] + hydrogen bonds. A particular role of the unusual anharmonicity expressed in the isotopic ratio ISR ≫ $\sqrt 2 $ is discussed when the fundamental vibrational levels are close to the barrier top for proton/deuteron motion. Copyright © 2007 John Wiley & Sons, Ltd.