scholarly journals Dipole Moments and Nuclear Quadrupole Coupling Constants of Alkyl Halides

1958 ◽  
Vol 31 (7) ◽  
pp. 832-837
Author(s):  
Hidekazu Hamano
Keyword(s):  
Dipole Moments ◽  
Alkyl Halides ◽  
Coupling Constants ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole

Aspects of hybridization

1950 ◽  
Vol 202 (1071) ◽  
pp. 548-564 ◽  
Keyword(s):  
Dipole Moments ◽  
Atomic Orbital ◽  
Second Order ◽  
Coupling Constants ◽  
Covalent Bonds ◽  
Orbital Hybridization ◽  
Quadrupole Coupling ◽  
Orbital Approximation ◽  
Nuclear Quadrupole ◽  
Oxygen Atoms

It has been shown that the pairing theory of orbital hybridization accounts satisfactorily for the variations which are observed in the properties of C-H bonds. Since heteropolar effects are in the opposite directions to the effects described, it is concluded that hybridization influences the properties of predominantly covalent bonds to a greater extent than do differences in electronegativity. The extent of second-order hybridization in the molecules CH, NH and OH has been dealt with in the light of this analysis. The consequences of the electronegativity concept have been examined on the basis of a generalized atomic orbital approximation. In particular, variations of the electronegativity of the carbon, nitrogen and oxygen atoms in different states of hybridization have been analyzed. The idea of 'lone' electrons has been formalized and the results of this definition have been discussed. Finally, the effects of orbital hybridization on the dipole moments and nuclear quadrupole coupling constants of molecules have been considered.

The Charge Distribution in Amides and Thioamides by Nuclear Quadrupole Coupling, Dipole Moments and Electronic Structure Calculations

1996 ◽  
Vol 51 (5-6) ◽  
pp. 460-478
Author(s):  
Michael H. Palmer ◽  
Paul Sherwood
Keyword(s):  
Dipole Moments ◽  
Lone Pair ◽  
Coupling Constants ◽  
Hartree Fock ◽  
Quadrupole Coupling ◽  
Quadrupole Resonance ◽  
Electron Contribution ◽  
Nuclear Quadrupole ◽  
Moller Plesset ◽  
Structure Calculations

AbstractThe nuclear quadrupole coupling constants from microwave spectroscopy (MW) and quadrupole resonance (NQR) for amides and thioamides are discussed in relation to Hartree-Fock calculations with and without Moller-Plesset correlation effects. The view that the larger dipole moments from thioamides than the corresponding amides is a function of enhanced resonance in the former is discussed and (in effect) confirmed by the present procedures. The principal mechamism seems to be the push/pull π/σ effects of the N atom with respect to the CO and CS groups, with S being a better σ-donor than O; however, the effect is still present with formamidine where no electronegativity effects are important, so the overall effect is the 2,1,1 π-electron contribution to the allylic system from N, C, O(S). The use of localised MO’s and NO’s is described, and the centroid positions are discussed in relation to the polarity of the bonds. The LMO’s largely truncate the contributions to each NQCC to the three attached bonds (or 2 bonds + a lone pair orbital at O or S), as is used in the Townes-Dailey procedures. More distant LMO’s generally contribute < 0.05 a. u. to the EFG, simplifying the analysis. The effects of O( or S)-protonation of urea and thiourea is discussed.

19F Nuclear Quadrupole Coupling in some Halomethanes

1986 ◽  
Vol 41 (1-2) ◽  
pp. 171-174 ◽  
Author(s):  
M. Frank ◽  
F. Gubitz ◽  
W. Ittner ◽  
W. Kreische ◽  
A. Labahn ◽  
...  
Keyword(s):  
Angular Distribution ◽  
Simple Model ◽  
Temperature Dependence ◽  
Coupling Constants ◽  
Temperature Dependent ◽  
Distribution Method ◽  
Quadrupole Coupling ◽  
Time Differential ◽  
Nuclear Quadrupole

The 19F quadrupole coupling constants in CF4, CHF3, CClF3 and CHClF2 are reported. The measurements were carried out temperature dependent using the time differential perturbed angular distribution method (TDPAD). The temperature dependence can be satisfactorily described in the framework of the Bayer-Kushida theory. A simple model is used to explain the appearance of H-F and Cl-F coupling constants in CHF3/CHClF2 and CClF3, respectively.

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