PROTON-TRANSFER AND SECONDARY DEUTERIUM-ISOTOPE EFFECT IN THE C-13 NMR-SPECTRA OF ORTHO-AMINOMETHYL PHENOLS

The temperature dependence of the deuterium isotope effect on the C-13 NMR signals for various positions in the phenyl ring of 2-(N,N-diethy laminomethyl) tetrachlorophenol was studied in the moderately polar so lvent CH2Cl2. The critical temperature, T-c = 245 K, corresponds to th e compensation of opposite effects for non-proton-transfer and proton- transfer (PT) forms existing in equilibrium. The UV spectra show that the contribution of the PT form at 245 K amounts to 20 +/- 5%. Semi-em pirical calculations taking into account the Onsager reaction field al lowed us to discuss the role of permittivity and dimerization of polar PT forms in the charge separation.