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@ARTICLE{Huschek:716,
      author       = {Huschek, G. and Hollmann, D. and Kurowski, N. and
                      Kaupenjohann, M. and Vereecken, H.},
      title        = {{R}e-evaluation of the conformational structure of
                      sulfadiazine species using {NMR} and ab initio {DFT} studies
                      and its implication on sorption and degradation},
      journal      = {Chemosphere},
      volume       = {72},
      issn         = {0045-6535},
      address      = {Amsterdam [u.a.]},
      publisher    = {Elsevier Science},
      reportid     = {PreJuSER-716},
      pages        = {1448 - 1454},
      year         = {2008},
      note         = {The authors gratefully acknowledge the financial support
                      provided by the German Research Foundation (DFG - Deutsche
                      Forschungsgemeinschaft) for Research Unit 566 Veterinary
                      Medicines in Soil. We would also like to thank Dr. A. Koch
                      for his excellent technical and analytical support.},
      abstract     = {In the environment, the sorption and the degradation of
                      organic pollutants are of increasing interest. The
                      investigation of the chemical structures provides a basis
                      for the development of a suitable binding model approach and
                      for the mechanistic understanding of the chemical fate
                      processes. The aim of this study was the identification of
                      different species of the antibiotic compound sulfadiazine
                      (SDZ) using (1)H and (13)C NMR experiments and ab initio
                      density functional theory (DFT) calculations. In the
                      neutral, aprotic solvent dimethylsulfoxide-d(6) (DMSO-d(6)),
                      a new sulfadiazine structure containing an O-H-N hydrogen
                      bond was identified. In the protic solvent water-d(2) and in
                      dependence on pH and the position of the amidogen hydrogen
                      atom nine possible SDZ conformations were analyzed and five
                      structures were identified. Good conformity between theory
                      and calculation of (1)H NMR was observed. Unfortunately,
                      (13)C NMR is not sensitive enough for comparison and
                      differentiation. In order to verify the identified
                      structures, additional NBO/NLMO (natural localized molecular
                      orbital) analyses were conducted (calculation of net atomic
                      charges, bond polarity, atomic valence, and electron
                      delocalization). Finally, conformation optimizations were
                      performed in order to investigate the stability of the SDZ
                      species. We showed that SDZ contains no S=O double bond, but
                      that it has two S-O single bonds. Surprisingly, negative
                      charges were observed at the pyrimidine nitrogen atom. With
                      these results, the known structure of SDZ was revised.
                      Studies of the geometrical structure and the torsion angles
                      showed that SDZ is very flexible and can be easily fitted to
                      the sorbent. These observations would explain the strong
                      sorbance and hence the rapid formation of non-extractable
                      residues in the environment because SDZ acts as a strong
                      ligand. These results show that that the sulfonamide
                      hydrogen is important for the biological activity but the
                      pyrimidine nitrogen and the sulfonamide oxygen is
                      responsible for the sorbance in environment.},
      keywords     = {Absorption / Hydrogen-Ion Concentration / Magnetic
                      Resonance Spectroscopy: methods / Models, Molecular /
                      Molecular Structure / Sulfadiazine: chemistry / Sulfadiazine
                      (NLM Chemicals) / J (WoSType)},
      cin          = {ICG-4 / JARA-ENERGY / JARA-SIM},
      ddc          = {333.7},
      cid          = {I:(DE-Juel1)VDB793 / $I:(DE-82)080011_20140620$ /
                      I:(DE-Juel1)VDB1045},
      pnm          = {Terrestrische Umwelt},
      pid          = {G:(DE-Juel1)FUEK407},
      shelfmark    = {Environmental Sciences},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:18602132},
      UT           = {WOS:000259166200008},
      doi          = {10.1016/j.chemosphere.2008.05.038},
      url          = {https://juser.fz-juelich.de/record/716},
}