Some Studies in Molecular Orbital Theory I. Resonance Structures and Molecular Orbitals in Unsaturated Hydrocarbons

1950 ◽  
Vol 18 (3) ◽  
pp. 265-274 ◽  
Author(s):  
H. C. Longuet‐Higgins
Keyword(s):  
Molecular Orbital ◽  
Molecular Orbitals ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Unsaturated Hydrocarbons ◽  
Resonance Structures

Molecular Orbitals and CH3, CH2, and CH Deformation Group Frequencies

1980 ◽  
Vol 34 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Norman B. Colthup
Keyword(s):  
Linear Relationship ◽  
Electron Density ◽  
Force Constant ◽  
Molecular Orbital ◽  
Interaction Force ◽  
Molecular Orbitals ◽  
Deformation Vibration ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Symmetrical Deformation

A linear relationship has been found between the wavenumber of the CH3 symmetrical deformation vibration and the electron density on the CH3 carbon as calculated from CNDO/2 molecular orbital theory. Other CH deformation vibrations are also related to the electron density on the carbon and, as a result, can be correlated with the CH3 symmetrical deformation wavenumber. These include ν̄(CH2 def), ν̄(CH2 wag) and both components of ν̄(CH wag). The splitting of ν̄(CH3 sym def) in isopropyl and t-butyl groups has long been known. It is shown here that the effect is due to an interaction force constant relating to the CH3 symmetrical deformation vibrations of two or three different neighboring CH3 groups. The origin of the interaction is thought to be an H,H′ repulsion between hydrogens on the different CH3 groups.

scholarly journals The determination of molecular orbitals

1949 ◽  
Vol 198 (1052) ◽  
pp. 1-13 ◽  
Keyword(s):  
Molecular Orbital ◽  
Molecular Orbitals ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Energy States ◽  
Molecular Framework

In the molecular orbital theory of valency the electrons are assigned to the whole molecule rather than to atoms or to other localized parts. While the method has advantages in dealing with the properties of a molecule as a whole, such as its energy states, the extension of each orbital over the molecular framework is a disadvantage when dealing with localized properties such as directed bonds. This paper deals in a general way with the equations which molecular orbitals must satisfy, allowing for the exchange of electrons between orbitals. It is then shown that when molecules have properties of symmetry the equations can be transformed so as to be satisfied by orbitals which have the property of equivalence. These can be regarded under certain conditions as directed orbitals and the conditions for these are discussed. To illustrate the method molecules of the type XY 2 are considered.

The molecular orbital theory of chemical valency. IV. The significance of equivalent orbitals

1950 ◽  
Vol 202 (1069) ◽  
pp. 166-180 ◽  
Keyword(s):  
Total Energy ◽  
Molecular Orbital ◽  
Molecular Orbitals ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
General Transformation ◽  
Lone Pairs ◽  
Simple Molecules

The theory of the transformation from molecular orbitals to sets of equivalent orbitals is discussed for the general case when there is more than one occupied molecular orbital of given symmetry and more than one equivalent set. The general transformation is worked out for molecules whose component atoms possess inner shells and lone pairs of electrons. The theory is illustrated by reference to some simple molecules such as water and ammonia. Finally, it is shown how the expression for the total energy of a molecule can be divided up in such a way that the interactions between its localized parts are dealt with separately. The significance of lone pairs of electrons in determining the shape of molecules is pointed out.

scholarly journals How amino and nitro substituents direct electrophilic aromatic substitution in benzene: an explanation with Kohn–Sham molecular orbital theory and Voronoi deformation density analysis

2016 ◽  
Vol 18 (17) ◽  
pp. 11624-11633 ◽  
Author(s):  
O. A. Stasyuk ◽  
H. Szatylowicz ◽  
T. M. Krygowski ◽  
C. Fonseca Guerra
Keyword(s):  
Molecular Orbital ◽  
Electrophilic Substitution ◽  
Molecular Orbitals ◽  
Electrophilic Aromatic Substitution ◽  
Molecular Orbital Theory ◽  
Aromatic Substitution ◽  
Orbital Theory ◽  
Deformation Density ◽  
Density Analysis

Molecular orbitals of aniline explain electrophilic substitution, whereas for nitrobenzene charge rearrangements are needed.

Perspectives on the Role of the Frontier Effective-for-Reaction Molecular Orbital (FERMO) in the Study of Chemical Reactivity: An Updated Review

2020 ◽  
Vol 24 (3) ◽  
pp. 314-331 ◽  
Author(s):  
Letícia S. Braga ◽  
Daniel H. S. Leal ◽  
Kamil Kuca ◽  
Teodorico C. Ramalho
Keyword(s):  
Molecular Orbital ◽  
Chemical Reactions ◽  
Chemical Reactivity ◽  
Molecular Orbitals ◽  
Frontier Molecular Orbital ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital

Molecular orbitals are critical in the rationalization of several chemical reactions. Thus, the frontier molecular orbital theory, proposed by Fukui's group, postulated the importance of the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO) for chemical reactions. It should be kept in mind, however, that there are limitations of this theory and new perspectives about the chemical reactivity have recently been arisen based on composition and location of other frontier molecular orbitals. In this review, we have reported the development and the most recent applications of the Frontier Effective-for-Reaction Molecular Orbital (FERMO) concept, which describes the breaking and formation of new chemical bonds and can in turn, provide important clues that modulate chemical reactivity of atoms and molecules.

The molecular orbital theory of chemical valency. III. Properties of molecular orbitals

1950 ◽  
Vol 202 (1069) ◽  
pp. 155-165 ◽  
Keyword(s):  
Perturbation Theory ◽  
Molecular Orbital ◽  
Molecular Orbitals ◽  
Molecular Properties ◽  
The Other ◽  
Molecular Orbital Theory ◽  
Special Significance ◽  
Orbital Theory ◽  
Molecular Systems ◽  
Normal States

The discussion of molecular orbitals and equivalent orbitals, given in previous papers, is carried a stage further. It is shown that certain molecular properties can be evaluated using either equivalent or molecular orbitals. On the other hand, a study of the changes produced by ionization demonstrates that molecular orbitals have a special significance and that certain energy parameters associated with them are closely related to ionization potentials. For the purpose of this discussion a perturbation theory is developed to deal with the changes produced in molecular systems when disturbed from their normal states.

THE HELLMANN–FEYNMAN THEOREM AND CHEMICAL BINDING

1961 ◽  
Vol 39 (6) ◽  
pp. 1253-1265 ◽  
Author(s):  
Richard F. W. Bader ◽  
Glenys A. Jones
Keyword(s):  
Molecular Orbital ◽  
Molecular Orbitals ◽  
Physical Significance ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Chemical Binding ◽  
Actual Fact ◽  
Conventional Calculation ◽  
Electrostatic Interpretation ◽  
Feynman Theorem

The advantages of the electrostatic interpretation of chemical binding are illustrated. It is shown that the forces exerted by the electrons in a molecular orbital may be determined by general expressions. These are functions of only one parameter, the value of which is easily specified for a particular case. From the general expressions it is possible to obtain quantitative measures of the bonding or antibonding power of a molecular orbital. It is shown that the usual interpretations of bonding and antibonding properties in molecular orbital theory are misleading and that few orbitals are, in actual fact, antibonding. If molecular orbitals are classified as netbonding or netantibonding, terms which are precisely defined and have a definite physical significance, a much closer correlation with previous concepts of bonding is obtained. The effects of mutual orthogonalization within a set of orbitals are studied. It is found that this procedure decreases the bonding ability of bonding orbitals, but increases that of antibonding orbitals. The dangers of disregarding such orthogonalization in a conventional calculation are clearly illustrated.

Bonding in Transition Metal Silyl Dimers. Molecular Orbital Theory

1989 ◽  
Author(s):  
Alfred B. Anderson ◽  
Paul Shiller ◽  
Eugene A. Zarate ◽  
Claire A. Tessier-Youngs ◽  
Wiley J. Youngs
Keyword(s):  
Transition Metal ◽  
Molecular Orbital ◽  
Molecular Orbital Theory ◽  
Orbital Theory
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