title: Geometries and tautomerism of OHN hydrogen bonds in aprotic solution probed by H/D isotope effects on (13)C NMR chemical shifts.
abstract: The (1)H and (13)C NMR spectra of 17 OHN hydrogen-bonded complexes formed by CH(3)(13)COOH(D) with 14 substituted pyridines, 2 amines, and N-methylimidazole have been measured in the temperature region between 110 and 150 K using CDF(3)/CDF(2)Cl mixture as solvent. The slow proton and hydrogen bond exchange regime was reached, and the H/D isotope effects on the (13)C chemical shifts of the carboxyl group were measured. In combination with the analysis of the corresponding (1)H chemical shifts, it was possible to distinguish between OHN hydrogen bonds exhibiting a single proton position and those exhibiting a fast proton tautomerism between molecular and zwitterionic forms. Using H-bond correlations, we relate the H/D isotope effects on the (13)C chemical shifts of the carboxyl group with the OHN hydrogen bond geometries.
authors.affiliation: Institute of Chemistry and Biochemistry, Free University of Berlin, Germany.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Tolstoy
authors.forename: Jing
authors.initials: J
authors.lastname: Guo
authors.forename: Benjamin
authors.initials: B
authors.lastname: Koeppe
authors.forename: Nikolai S
authors.initials: NS
authors.lastname: Golubev
authors.forename: Gleb S
authors.initials: GS
authors.lastname: Denisov
authors.forename: Sergei N
authors.initials: SN
authors.lastname: Smirnov
authors.forename: Hans-Heinrich
authors.initials: HH
authors.lastname: Limbach
mesh_terms: D019342:Acetic Acid / Q000737:chemistry*; D002247:Carbon Isotopes / Q000737:chemistry*; D003903:Deuterium / Q000737:chemistry*; D006860:Hydrogen Bonding; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D009584:Nitrogen / Q000737:chemistry*; D009587:Nitrogen Isotopes / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry*; D011522:Protons; D011725:Pyridines / Q000138:chemical synthesis; D012996:Solutions; D013696:Temperature
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D011522:Protons; D011725:Pyridines; D012996:Solutions; D003903:Deuterium; D009584:Nitrogen; D019342:Acetic Acid; D010100:Oxygen