scholarly journals A Theoretical Study of the Conformational Changes in Hydrazine

1974 ◽  
Vol 52 (15) ◽  
pp. 2785-2791 ◽  
Author(s):  
John O. Jarvie ◽  
Arvi Rauk
Keyword(s):  
Dihedral Angle ◽  
Conformational Changes ◽  
Theoretical Study ◽  
Potential Surface ◽  
Experimental Results ◽  
Hartree Fock ◽  
Pyramidal Inversion ◽  
Bond Functions ◽  
Torsional Component ◽  
Substituted Hydrazines

Abinitio restricted Hartree–Fock–Roothaan l.c.a.o.–m.o.–s.c.f. calculations using a Gaussian lobe basis with bond functions have been performed to determine the characteristics of the potential surface for nuclear motions in hydrazine. It was found that in its equilibrium conformation the molecule has a dihedral angle of 95°. The barrier to pyramidal inversion at one nitrogen is 6.1 kcal/mol and the syn and anti rotational barriers are calculated to be 12.0 and 1.6 kcal/mol, respectively. There is a very slight torsional component in the inversion pathway. During rotation over the anti barrier the bond angles contract from their average equilibrium value of 109.5° to 105.3°. This contraction appears to be an important feature of the rotational potential curve. Features of the surface are used to rationalize experimental results in cyclic and acyclic substituted hydrazines.

scholarly journals Theoretical Study of the Electronic Effects in the Intramolecular Ketene-Styrene [2+2] Cycloaddition

2019 ◽  
Vol 54 (4) ◽  
Author(s):  
Manuel Fernando Rubio ◽  
Federico Jiménez-Cruz ◽  
Guillermo Ramírez-Galicia
Keyword(s):  
Transition State ◽  
Theoretical Study ◽  
Positive Charge ◽  
Ring Structure ◽  
Experimental Results ◽  
Electronic Effects ◽  
Hartree Fock ◽  
Reaction Constant ◽  
Remote Substituent

DFT (B3LYP/6-31+G*) and post-Hartree-Fock (MP2/6-31+G*//B3LYP/6-31G*) calculations were carried out in order to explain the effect of a remote substituent in the intramolecular ketene-styrene [2+2] cycloaddition of p-substituted 2-methyl-7-arylhepta- 1,6-dien-1-one which produces the bicycle[3.1.1] or the bicycle [3.2.0] heptanones according to Bèlanger experimental results. The transition state geometries were found as an asynchronous process with a three-member ring structure and an incipient positive charge development. Kinetic and thermodynamic controls were proposed at B3LYP/6-31+G* to determine which product is most likely to form in a competence reaction. In addition, the value of the ρ experimental reaction constant was reproduced, ρ ~ -1.34.

A theoretical study on the stereochemistry and protonation of −:CH2—NO2

1976 ◽  
Vol 54 (16) ◽  
pp. 2526-2533 ◽  
Author(s):  
P. G. Mezey ◽  
A. J. Kresge ◽  
I. G. Csizmadia
Keyword(s):  
Molecular Conformation ◽  
Theoretical Study ◽  
Negative Charge ◽  
Potential Surface ◽  
Population Analysis ◽  
Substantial Portion ◽  
Mulliken Population ◽  
Pyramidal Inversion ◽  
Pyramidal Configuration ◽  
A Charge

The molecular conformation of −:CH2NO2 is found to be planar with an extremely shallow potential curve to pyramidal inversion. This suggests that suitable substituents could conceivably perturb the System into a pyramidal configuration corresponding to double minimum on the potential surface and that a chiral carbanion might therefore exist. Rotating the NO2 group out of planarity by 90° raises the barrier to inversion at carbon by an appreciable amount.A Mulliken population analysis gives a charge distribution in which a substantial portion of the negative charge has shifted from carbon to oxygen; this is consistent with the well-known tendency of nitronate ions to undergo simultaneous competitive protonation on carbon and oxygen.

Nuclear magnetic resonance microscopy with 4-μm resolution: Theoretical study and experimental results

1988 ◽  
Vol 15 (6) ◽  
pp. 815-824 ◽  
Author(s):  
Z. H. Cho ◽  
C. B. Ahn ◽  
S. C. Juh ◽  
H. K. Lee ◽  
R. E. Jacobs ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Theoretical Study ◽  
Experimental Results ◽  
Magnetic Resonance Microscopy ◽  
Nuclear Magnetic

Structural and conformational changes in [M(1,10-diaza-18-crown-6)Cl2] (M = Pd, Pb) complexes: a crystallographic and theoretical study

CrystEngComm ◽  
2018 ◽  
Vol 20 (42) ◽  
pp. 6733-6740 ◽  
Author(s):  
Antonino Arenaza-Corona ◽  
David Morales-Morales ◽  
Iran F. Hernández-Ahuactzi ◽  
Victor Barba
Keyword(s):  
Conformational Changes ◽  
Theoretical Study ◽  
Solvent System ◽  
Selection Of ◽  
Solvent Solvent

The appropriate selection of a given solvent/solvent system influences directly the molecular conformational structures of MLX2 complexes.

PERIODIC HARTREE–FOCK CALCULATION OF THE OXIDATION OF Si(111)

1999 ◽  
Vol 06 (06) ◽  
pp. 1031-1036 ◽  
Author(s):  
PHILIPPE SONNET ◽  
LOUISE STAUFFER ◽  
CHRISTIAN MINOT
Keyword(s):  
Oxygen Atom ◽  
Local Minimum ◽  
Atomic Oxygen ◽  
Potential Surface ◽  
Early Stage ◽  
Heat Of Adsorption ◽  
Molecular Adsorption ◽  
Hartree Fock

We present Hartree–Fock calculations of the adsorption of oxygen on a Si(111)-(2×2) surface, which models the Si(111)-(7×7) structure, including its two main sites (adatom and rest atom sites). In the most stable configurations, molecules dissociate leading to atomic oxygen bridging the adatom backbonds. The molecular adsorption is less favorable. The dioxygen, however, is a local minimum of the potential surface in two cases: (i) in the "grif" geometry; (ii) bridging between a rest atom and an adatom. It then represents a possible precursor for the early stage of oxidation. The presence of an oxygen atom already adsorbed on the surface enhances the heat of adsorption of other oxygen (atomic or molecular) on the same site.

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