Shape of the proton potential in an intramolecular hydrogen-bonded system

5,5'-dibromo-3-diethylaminomethyl-2,2'-biphenol N-oxide was studied by IR a nd NMR spectroscopy in chloroform and acetonitrile solutions. Two intramole cular hydrogen bonds are present in these molecules. The NO...H+...O- bond formed between the OH and the N-oxide groups is very strong. The proton pot ential is flat and broad and has probably no barrier. This hydrogen bond sh ows only slight proton polarizability. The other hydrogen bond formed betwe en two hydroxyl groups OH...O- reversible arrow (-) O...HO is weaker and sh ow large proton polarizability. The proton motions in both hydrogen bonds a re not coupled and therefore these hydrogen bonds are not cooperative. (C) 2001 Elsevier Science B.V. All rights reserved.