scholarly journals Challenges in Studying Steric Interactions in Highly Strained Perhalogenated Alkanes and Silanes.

2021 ◽  
Author(s):  
Luís Simões ◽  
RODRIGO CORMANICH
Keyword(s):  
Quantum Theory ◽  
Total Energy ◽  
Homologous Series ◽  
Nbo Analysis ◽  
Steric Effects ◽  
Electrostatic Effects ◽  
Steric Interactions ◽  
Stereoelectronic Effects ◽  
Helical Geometry ◽  
Highly Strained

The decomposition of the molecular total energy in their hyperconjugative, steric and electrostatic effects can lead to interesting interpretations about the stereoelectronic effects that govern their geometry and properties. In this work, we have studied homologous series of perfluoroalkanes, perchloroalkanes, perfluorosilanes and perchlorosilanes, and all molecules have preference for helical geometries. According to Natural Bond Orbitals (NBO) calculations, the silanes have their helical geometry stabilised by hyperconjugative interactions, as well as the perfluoroalkanes. However, it was surprisingly difficult to disclose that steric interactions are ruling the helical geometry preference in perchloroalkanes by comparing the NBO analysis and the Quantum Theory of Atoms ins Molecules (QTAIM). Although perchloroalkanes have extremely intense steric interactions between Cl lone pairs, some of them were underestimated by the NBO analysis, which showed the opposite behaviour compared with QTAIM that indicates steric effects as the leading forces to helical geometry preference.

scholarly journals The quantum theory and the dielectric constant

1924 ◽  
Vol 105 (734) ◽  
pp. 650-661 ◽  
Keyword(s):  
Dielectric Constant ◽  
Quantum Theory ◽  
Electric Field ◽  
Total Energy ◽  
Quantum Number ◽  
Quantum Numbers

The change of energy of an atom of hydrogen when submitted to an electric field has been calculated by Epstein. If W denotes the total energy of an atom, then the change in energy Δ W, due to the field F, is given by ΔW = - 3 h 2 F/8 π 2 m E ( n 2 - n 1 ) ( n 1 + n 2 + n 3 ) + 17 e 2 F 2 /(16 π R H ) 2 m Z ( n 1 , n 2 , n 3 ), where R H is Rydberg's constant for hydrogen and Z ( n 1 , n 2 , n 3 ) = ( n 1 + n 2 + n 3 ) 6 {1 - 3/17 ( n 1 - n 2 /( n 1 + n 2 + n 3 ) 2 - 9/17 ( n 3 / n 1 + n 2 + n 3 ) 2 }, and n 1 and n 2 are parabolic quantum numbers and n 3 is the equatorial quantum number.

1,7-Dioxaspiro[5.5]undecanes. An excellent system for the study of stereoelectronic effects (anomeric and exo-anomeric effects) in acetals

1981 ◽  
Vol 59 (7) ◽  
pp. 1105-1121 ◽  
Author(s):  
Pierre Deslongchamps ◽  
Daryl D. Rowan ◽  
Normand Pothier ◽  
Gilles Sauvé ◽  
John K. Saunders
Keyword(s):  
Experimental Results ◽  
Nmr Analysis ◽  
Steric Interactions ◽  
Stereoelectronic Effects ◽  
Anomeric Effects ◽  
Acid Cyclization ◽  
C Nmr

Several isomeric compounds derived from the spiro systems 5 to 9 (Scheme 4) were obtained from the acid cyclization of the appropriate dihydroxy ketone precursor.The configuration and the conformation of the products obtained was determined by 13C nmr analysis and equilibration studies. The experimental results can be rationalized by taking into account the anomeric and the exo-anomeric effects and the usual steric interactions.

scholarly journals Theoretical insights into the properties of the borazine… X- complexes (X- = H, F, Cl, CN, NC or NCO)

2009 ◽  
Vol 74 (10) ◽  
pp. 1105-1111 ◽  
Author(s):  
Reza Ghiasi
Keyword(s):  
Charge Transfer ◽  
Chemical Shift ◽  
Total Energy ◽  
Ab Initio ◽  
Intermolecular Interactions ◽  
Natural Bond Orbital ◽  
Nbo Analysis ◽  
Interaction Energies ◽  
Ab Initio Method ◽  
Nucleus Independent Chemical Shift

The character of the NH ...X- (X- = H, F, Cl, CN, NC or NCO) interactions of borazine with anions was studied using ab initio method. The interaction energies were calculated at the B3LYP/6-311++G(d,p) level. The energetic and geometric characteristics of the complexes were compared. The 'atoms in molecules' methodology was used to analyze the electron density and to obtain atomic contributions to the total energy and charge of the systems. Natural bond orbital (NBO) analysis demonstrated the charge transfer in the study of the nature of the intermolecular interactions. The aromaticity of these compounds was predicted in light of the nucleus-independent chemical shift (NICS).

A Computational Study of the Conformational Behavior of 2,5-Dimethyl- 1,4-dithiane-2,5-diol and Analogous S and Se: DFT and NBO Study

2020 ◽  
Vol 17 (10) ◽  
pp. 749-759
Author(s):  
Elmira Danaie ◽  
Shiva Masoudi ◽  
Nasrin Masnabadi
Keyword(s):  
Thermodynamic Parameters ◽  
Computational Study ◽  
Structural Parameters ◽  
Nbo Analysis ◽  
Electron Delocalization ◽  
Stereoelectronic Effects ◽  
Conformational Properties ◽  
Molecular Reactivity ◽  
Stabilization Energies ◽  
The Stability

Conformational behaviors of 2,5-dimethyl-1,4-dithiane-2,5-diol (compound 1), 2,5- dimethyl-1,4-dithiane-2,5-dithiol (compound 2) and 2,5-dimethyl-1,4-dithiane-2,5-diselenol (compound 3) were investigated by the B3LYP/6-311+G **, the M06-2X/aug-ccpvdz levels of theory and natural bond orbital NBO analysis. The structures and the structural parameters of the mentioned molecules were optimized by the B3LYP and the M06-2X methods. We assessed the roles and contributions of the effective factors in the conformational properties of the mentioned compounds by means of the B3LYP and M06-2X levels of theory and the NBO interpretations. The stereoelectronic effects of the mentioned molecules were studied using the NBO analysis. The results showed that the stereoelectronic effects were in favor of the (ax,ax) conformers (the most stable conformations), from compound 1 to compound 3; therefore, these effects have impacts on the conformational properties of compounds 1-3, and stabilization energies associated with LP2X→ σ*S1-C2 electron delocalization, where [X= O, S, and Se], for 1-ax, ax conformer has the greatest value between all of the other conformers. Therefore, according to the calculated thermodynamic parameters, the stability of the 1-ax, ax compound was justified by the presence of LP2X→σ*S1-C2 electron delocalization. A molecular orbital explanation was conducted to investigate the correlations between the linear combinations of natural bond orbitals in the HOMOs, LUMOs and the molecular reactivity parameters. There is a direct relationship between the stereoelectronic effects, molecular reactivity and thermodynamic parameters of compounds 1 to 3 as the harder ax, ax conformations with the greater stereoelectronic effects and ΔG(eq-ax) values are more stable than their corresponding eq, eq conformers. Besides frontier molecular orbitals (FMOs), mapped molecular electrostatic potential (MEP) surfaces of conformations of compounds 1 to 3 were investigated.

The quantum theory of lattice dynamics. Il

1969 ◽  
Vol 310 (1500) ◽  
pp. 89-99 ◽  
Keyword(s):  
Quantum Theory ◽  
Total Energy ◽  
Ground State ◽  
Lattice Dynamics ◽  
Equilibrium Configuration ◽  
Third Order ◽  
Hartree Fock

Expressions are derived for the expansion of the total energy of the electrons in their ground state in a crystal in powers of displacements of the nuclei from their equilibrium configuration. The expansion is taken up to third order on the basis of the coupled Hartree-Fock equations and thus one obtains expressions for the electronic contributions to the dynamical and anharmonic tensors.

1,7-Dithia and 1-oxa-7-thiaspiro[5.5]undecanes. Excellent systems for the study of stereoelectronic effects (anomeric and exo-anomeric effects) in the monothio and the dithioacetal functions

1981 ◽  
Vol 59 (7) ◽  
pp. 1122-1131 ◽  
Author(s):  
Pierre Deslongchamps ◽  
Daryl D. Rowan ◽  
Normand Pothier ◽  
John K. Saunders
Keyword(s):  
Experimental Results ◽  
Hydroxy Ketone ◽  
Nmr Analysis ◽  
Steric Interactions ◽  
Stereoelectronic Effects ◽  
Anomeric Effects ◽  
Acid Cyclization ◽  
C Nmr

1,7-Dithiaspiro[5.5]undecane (2), 1-oxa-7-thiaspiro[5.5]undecane (4), and the tricyclic systems 3, 5, and 6 have been prepared by the acid cyclization of the appropriate ketone dithiol or hydroxy ketone thiol precursors.The configuration and the conformation of the products obtained was determined by 13C nmr analysis and equilibration studies. The experimental results can be rationalized by taking into account the anomeric and the exo-anomeric effects and the usual steric interactions.

Synthèse et étude du réarrangement des diazoles-1,3: alkyl-1 alkylthio-2 (allylthio, arylthio, cycloalkylthio) imidazoles. Partie II. Réarrangement et réactions parasites

1979 ◽  
Vol 57 (7) ◽  
pp. 822-830 ◽  
Author(s):  
Jacky Kister ◽  
Georges Assef ◽  
Gilbert Mille ◽  
Jacques Metzger
Keyword(s):  
Structural Effect ◽  
Steric Effects ◽  
Steric Interactions ◽  
Ortho Effect ◽  
Rearrangement Reaction ◽  
Kinetics Of ◽  
Electronic And Steric Effects

The kinetics of the [Formula: see text] rearrangement reaction for a series of 1-alkyl-2-alkylthio (or allylthio, arylthio, cycloalkylthio) imidazoles has been studied at various temperatures. The rearrangement and hydrolysis results have been compared with those of 1-alkyl-2-methylthio-Δ-2-imidazolines and 1-alkyl-2-methylthio-Δ-2-tetrahydropyrimidines. Electronic and steric effects are discussed and a parallel between pKa and rearrangement is proposed. The limit of this parallel is either a structural effect such as direct (ortho effect) or indirect (cycle deformation) steric interactions or geometric modifications of the heterocycles studied (five- or six-membered cycles). All these results permitted the coherent choice of the amplification compound of a nonconventional photographic process.

Sign in / Sign up

Export Citation Format

Share Document