Affiliation:
1. Institute of Organic Chemistry, University of Regensburg, 93053 Regensburg, Germany
Abstract
From an academic and practical point of view, it is desirable to be able to assess the possibility of the proton exchange of a given molecular system just by knowing the positions of the proton acceptor and the proton donor. This study addresses the difference between intramolecular hydrogen bonds in 2,2′-bipyridinium and 1,10-phenanthrolinium. Solid-state 15N NMR and model calculations show that these hydrogen bonds are weak; their energies are 25 kJ/mol and 15 kJ/mol, respectively. Neither these hydrogen bonds nor N-H stretches can be responsible for the fast reversible proton transfer observed for 2,2′-bipyridinium in a polar solvent down to 115 K. This process must have been caused by an external force, which was a fluctuating electric field present in the solution. However, these hydrogen bonds are the grain that tips the scales precisely because they are an integral part of a large system of interactions, including both intramolecular interactions and environmental influence.
Subject
Inorganic Chemistry,Organic Chemistry,Physical and Theoretical Chemistry,Computer Science Applications,Spectroscopy,Molecular Biology,General Medicine,Catalysis
Reference98 articles.
1. Hynes, J.T., Klinman, J.P., Limbach, H.-H., and Schowen, R.L. (2007). Hydrogen-Transfer Reachtions, WILEY-VCH Verlag.
2. Kohen, A., and Limbach, H.-H. (2006). Isotope Effects in Chemistry and Biology, CRC Press.
3. Conformers, Energetics, and Basicity of 2,2‘-Bipyridine;Howard;J. Am. Chem. Soc.,1996
4. The crystal structure of 2,2′-bipyridine;Merritt;Acta Crystallogr.,1956
5. Bis(2,2′-bipyridyl)diisopropoxymolybdenum(II). Structural and Spectroscopic Evidence for Molybdenum-to-Bipyridyl π* Bonding;Chisholm;J. Am. Chem. Soc.,1981