Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: steric effects

Sortuj według:

Ogranicz wyniki do:

Statistical Analysis of Consequences of peri-Interactions in 1-Si, 8-N- (and 1-X, 8-Y-) Substituted Naphthalenesin 1-Si, 8-N- (and 1-X, 8-Y-) Substituted Naphthalenes

Dominiak P., Schiemenz G., Woźniak K.

Polish Journal of Chemistry

2007

Vol. 81, nr 5-6

663-681

A statistical analysis of geometrical parameters for 1-Si, 8-N-substituted naphthalenes retrieved from the CSD revealed three factors describing structural consequences of peri interactions in such derivatives. The most important of them is an in-plane deformation whichmay be estimated by a linear combination of several geometrical parameters of the naphthalene fragment. It is best approximated by values of splay angles. The second consequence is an out-of-plane deformation formally defined by all torsion angles. It is well approximated by the Si–C(1)…C(8)–N torsion angle. The third factor can be associated with substituent effects and it manifests itself mainly by changes of Car-N/Si bond lengths and their ipso angles. Similar analysis performed for a more general data set consisting of 1-X, 8-Y-disubstituted naphthalenes fully supports the above interpretation. The peri X…Y distance (PD) can be expressed as linear combinations of the factors obtained, which leads to a multiple regression line with the value of the free term very close to PD and coefficients being relative weights of particular factors. It appears that in plane deformation contributes to the d(X...Y) distance farmore significantly than the other factors.

Intrinsic deuterium isotope effects on NMR chemical shifts of hydrogen bonded systems

Hansen P.

Nukleonika

2002

Vol. 47,suppl.1

37-42

This mini review describes intrinsic deuterium isotope effects on 13C chemical shifts of rigid hydrogen bonded compounds primarily in solution. The steric effects of intramolecularly hydrogen bonded compounds are dissected into different bond interactions leading either to steric compression or to steric twist. One-bond isotope effects involving CH(D) bonds are analyzed in terms of substituent effects and the question is raised whether isotope effects can be useful in the study of CHhydrogen bonds.