H-1 NMR study of proton motion in hydrogen-bonded chain in Mannich base of5,5 '-dibromo-3-diethylaminomethyl-2,2 '-biphenol

5,5'-dibromo-3-diethylaminomethyl-2,2'-biphenol was synthesized and the col lective proton motion in two intramolecular hydrogen bonds was studied by H -1 and C-13 NMR as well as by FTIR spectroscopy in chloroform. acetonitrile and chloroform containing traces of water solutions. In dry chloroform, al ways, two separated proton signals for the two OH groups were observed. If traces of water were present at room temperature in the chloroform solution only one signal for the two OH protons was found. With decreasing temperat ure the collective proton motion, indicated by continuous absorption in the FTIR spectrum, was interrupted and two separate signals appeared in the 1H NMR spectrum. In acetonitrile the collective proton motion in the two intr amolecular hydrogen-bonded system observed at room temperature vanished wit h decreasing temperature and finally only a cooperative hydrogen-bonded sys tem, like in the solid start, was observed. (C) 2001 Elsevier Science B.V. All rights reserved.