1H NMR Investigation of the Collective Proton Motion in Hydrogen-Bonded Systems of Monoaurates of 2,6-Bis((diethylamino)methyl)-4-R-phenols

Article abstract of DOI:10.1021/j100195a012

Eleven mono- and diaurates of 2,6-bis((diethylamino)methyl)-4-R-phenols were studied in CD2Cl2 solutions using 1H NMR spectroscopy.With the monoaurates a collective proton fluctuation occurs in the intramolecular hydrogen-bonded system as known from IR results.With increasing acidity of the phenolic group a low field shift of the signal of the hydrogen-bonded protons is found, indicating increasing deshielding.The protons are most strongly deshielded in the R = Cl system, from which is known that it shows the largest proton polarizability.With further increasing acidity the protons are more and more shielded by the N atoms.When the proton limiting structure in which the hydrogen-bonded protons are preferentially present at the N atoms becomes realized, the signals of the Ph-CH2 and the N-CH2 protons are strongly broadened.When the protons are almost localized at these N atoms, a doublet and an octet, respectively, are observed.These effects arise due to spin-spin coupling between the methylene protons and the NH⁺ protons.