DBU-promoted HBr-eliminations of a variety of vicinal dibromides having an adjacent heteroatom (F, O, or N) under mild basic conditions and relevant theoretical calculations were carried out. These HBr-eliminations proceeded more or less regioselectively, and all associated calculation results agreed with the experimental facts. This work suggests that the HBr-elimination selectivity is an effect of the electronegativity of the neighboring heteroatoms themselves rather than the electron-withdrawing effects of the entire heterofunctional group. 相似文献
Temporal evolution of electronegativity and hardness associated with a collision process between a Be atom and a proton has
been studied within a quantum fluid density functional framework. In the presence of a third collisional partner to take away
excess energy, this collision may lead to a chemical reaction producing a BeH+ molecule. For comparisonab initio SCF level calculation (with 6–31G** basis set) on BeH+ molecule with different geometries have been performed. Electronegativity equalization and maximum hardness principles are
analyzed. 相似文献
ABEEM/MM model has been applied to compute the various properties characterizing water clusters (H2O)n (n = 7−10), such as optimized geometries, the hydrogen bonds number, cluster interaction energies, stabilities, ABEEM charge
distributions, dipole moments, structural parameters, and so on, and to describe the transition reflected by the hexamer region
from two-dimensional (from dimer to pentamer) to three-dimensional structures (for clusters larger than the hexamer).
Supported by the National Natural Science Foundation of China (Grant No. 20373021) 相似文献
The possible genesis of negative atom condensed Fukui functions is discussed based on hardness kernel matrix relationships. The recent hypothesis that diagonal dominance of the hardness matrix is a requirement for positive Fukui functions is proven, and general considerations also predict the possibility of regions with numerically unstable Fukui functions, including discontinuities. 相似文献
We present a preliminary work for a general method of computing the partition of σ and π electronic effects of a given atom A or substituent R on a given substrate. In this aim, the nuclear charge Z* of a fictitious hydrogen atom H* is fitted in order that the A–H* (or R–H*) bond be purely covalent, i.e. the Mulliken electron population be one electron on H*. We obtain this way entities of the same electronegativity as A or R, thus having a comparable σ effect, without any π effect.
The values of Z* obtained for A–H* diatomic molecules (A=H–Br) exhibit a good linear correlation with the Allred–Rochow scale of electronegativity, as it could be expected on theoretical grounds. The method, applied to R–H* molecules, allows a determination of the electronegativity of a variety of polyatomic R substituents, and provides H*(R) having the same inductive effect as R. These results are discussed by comparison with some previous theoretical and experimental data.
As an example of application, the partition of σ and π contributions of R on the 13C chemical shifts in a series of monosubstituted benzenes RC6H5 has been computed. 相似文献