@article{KleinpeterFrank2009,
  author    = {Kleinpeter, Erich and Frank, Andrea},
  title     = {Distinction of Push,pull effect and steric hindrance in disubstituted alkynes},
  issn      = {0040-4020},
  doi       = {10.1016/j.tet.2009.03.075},
  year      = {2009},
  abstract  = {The push,pull effect in two series of disubstituted alkynes was studied at the DFT level [B3LYP/6-311G(d)] by application of the 13C chemical shift differences (GIAO) between the alkyne carbon atoms (Delta delta (C C)), the charge difference between these carbons (Delta q(C C)), the occupation quotient (NBO) of anti-bonding pi*, and bonding pi orbitals (pi*(C C)/pi(C C)) and the bond length (d(C C)) of the C C triple bond. The linear dependence of d(C C) versus pi*(C C)/pi(C C) quantifies changes in the push,pull effect while deviations from the latter correlation indicate and ascertain quantitatively to what extent steric hindrance restricts the strain-less conjugation of the C C triple bond pi- orbitals in the disubstituted alkynes.},
  language  = {en}
}
@article{KleinpeterFrank2009,
  author    = {Kleinpeter, Erich and Frank, Andrea},
  title     = {Quantification of the push-pull effect in substituted alkynes : evaluation of +/- I/+/- M substituent effects in terms of C C bond length variation},
  issn      = {1089-5639},
  doi       = {10.1021/Jp9024359},
  year      = {2009},
  abstract  = {C-13 chemical shifts of alkynes, published to date, were computed at the DFT (B3LYP/6-311G*) level of theory and compared with the experimental delta values, and the agreement was employed as a measure of quality for the underlying structures. For the corresponding global minima structures, thus obtained, the occupation quotients of antibonding pi* and bonding pi orbitals (pi*(C C)/pi(C C)) and the bond lengths (d(C C)) of the central C C triple bond were computed and correlated to each other. The linear dependence obtained for the two push-pull parameters d(C C) and pi*(C C)/pi(C C) quantifies changes in the push-pull effect of substituents while deviations from the best line of fit indicate and ascertain quantitatively to what extend the inductive (+/-l) substituent effect changes with respect to the bond length of the C C triple bond.},
  language  = {en}
}
@article{KleinpeterBoelkeFrank2008,
  author    = {Kleinpeter, Erich and B{\"o}lke, Ute and Frank, Andrea},
  title     = {Polar substituent effect of the ester group on conformational equilibria of O-mono-substituted cyclohexanes{\`u}the para-substituent effect in cyclohexyl benzoates},
  doi       = {10.1016/j.tet.2008.07.024},
  year      = {2008},
  abstract  = {Together with the nonsubstituted reference compound, para-methoxy- and para-nitro cyclohexyl benzoates have been synthesized and their conformational equilibria studied by low temperature NMR spectroscopy and theoretical DFT calculations. The free energy differences ;G° between axial and equatorial conformers were examined with respect to polar substituent influences on the conformational equilibrium of O-mono-substituted cyclohexane.},
  language  = {en}
}