@article{YonedaLealSeidletal.2007,
  author    = {Yoneda, Julliane Diniz and Leal, Katia Zaccur and Seidl, Peter Rudolf and Azeredo, Rodrigo Bagueira de V. and Kleinpeter, Erich},
  title     = {Camphor : a good model for illustrating NMR techniques},
  year      = {2007},
  abstract  = {CAMPHOR: A GOOD MODEL FOR ILLUSTRATING NMR TECHNIQUES. The use of Nuclear Magnetic Resonance spectroscopy to establish the three-dimensional structures of molecules is an important component of modern Chemistry courses. The combination of techniques that can be used for this purpose is conveniently illustrated by their application to the camphor molecule. This paper presents applications of several techniques used in NMR spectral interpretation in an increasing order of complexity. The result of individual experiments is illustrated in order to familiarize the user with the way connectivity through bonds and through space is established from 1D/2D-NMR spectra and molecular stereochemistry is determined from different NMR experiments},
  language  = {en}
}
@article{SeidlCarneiroTostesetal.2005,
  author    = {Seidl, Peter Rudolf and Carneiro, J. W. D. and Tostes, J. G. R. and Koch, Andreas and Kleinpeter, Erich},
  title     = {Interpretation of conformational effects on 2-endo-norborneol by natural chemical shielding analysis},
  issn      = {1089-5639},
  year      = {2005},
  abstract  = {This paper represents an extension of our work on the H-1 and C-13 NMR chemical shifts of norbornane and 2-endo- norborneol. NCS-NBO analysis was employed to probe contributions of bond orbitals and orbitals of lone pairs to nuclear shielding in conformers of the alcohol generated by rotation of the C-O bond. Variations in H-1 and C-13 chemical shifts with the dihedral angle are discussed in terms of Lewis and non-Lewis partitioning and their respective importance is evaluated. In addition to hyperconjugation of the lone pair in a p orbital of oxygen that was previously reported, a sizable participation of the lone pair which is in an sp orbital is also observed and their combined effect dominates the carbon chemical shifts of the C-1-C-2-OH and C-3-C-2-OH fragments. Both lone pairs on oxygen also contribute to localized, though-space effects on nuclei in the vicinity, these effects answering for the largest deviations in hydrogen chemical shifts on rotation around the C-O bond. On the other hand, for conformers in which nonbonded repulsions lead to distortions in the molecular framework, variations in chemical shifts may be attributed to angular effects},
  language  = {en}
}
@article{KleinpeterSeidl2005,
  author    = {Kleinpeter, Erich and Seidl, Peter Rudolf},
  title     = {The gamma- and the delta-effects in C-13 NMR spectroscopy in terms of nuclear chemical shielding (NCS) analysis},
  issn      = {0894-3230},
  year      = {2005},
  language  = {en}
}
@article{KleinpeterSeidl2004,
  author    = {Kleinpeter, Erich and Seidl, Peter Rudolf},
  title     = {The gamma- and the delta-effects in C-13 NMR spectroscopy in terms of nuclear chemical shielding (NCS) analysis},
  year      = {2004},
  abstract  = {Carbon-13 NMR is widely used in the determination of the stereochemistry of organic compounds. Changes in chemical shifts caused by interactions of groups that are close in space normally result in shielding of the carbon and deshielding of the hydrogen nuclei that are involved. This is not always the case, however, and further work on the origin of these effects would be desirable. Early applications of theoretical methods to the study of NMR shielding parameters were not particularly successful, but in recent years, the calculation of NMR shielding parameters by theoretical methods has developed into a useful and popular tool for structural studies by NMR. A promising approach to the problem of distinguishing and evaluating stereochemical influences on carbon and hydrogen chemical shifts is provided by natural chemical shielding (NCS) analysis. This method allows a partitioning of theoretical NMR shieldings into magnetic contributions from bonds and lone pairs of the molecule using the natural bond orbital (NBO) method. In order to investigate the origins of steric effects, we employed the NCS analysis to axial/equatorial-Me-cyclohexane, norbornane and exo/endo-Me-norbornane, in addition to n-pentane in the anti, gauche and g(P) g(M) conformations. Our results indicate that distortions in molecular structure due to steric effects can result in bond stretching or compression or in angular distortions. Changes in bond lengths result in the predictable shielding or deshielding of the nuclei that are involved. Where the molecular framework may be distorted to alleviate strain, chemical shifts appear to reflect changes in angles. Copyright (C) 2004 John Wiley Sons, Ltd},
  language  = {en}
}