Hydrogen molecular orbital theory

Valence bond and molecular orbital theory both incorporate the wave description of an atom s electrons into this picture of H2 but m somewhat different ways Both assume that electron waves behave like more familiar waves such as sound and light waves One important property of waves is called interference m physics Constructive interference occurs when two waves combine so as to reinforce each other (m phase) destructive interference occurs when they oppose each other (out of phase) (Figure 2 2) Recall from Section 1 1 that electron waves m atoms are characterized by their wave function which is the same as an orbital For an electron m the most stable state of a hydrogen atom for example this state is defined by the Is wave function and is often called the Is orbital The valence bond model bases the connection between two atoms on the overlap between half filled orbifals of fhe fwo afoms The molecular orbital model assembles a sef of molecular orbifals by combining fhe afomic orbifals of all of fhe atoms m fhe molecule... 

The opening pages of Chapter 10 introduce the principles of orbital overlap by describing molecular hydrogen as a composite of overlapping spherical 1 S orbitals. This Interaction Is the starting point for our discussion of molecular orbital theory. 

Molecular Orbital Theory Model. Oxygen and hydrogen atoms in H2O are held together by a covalent bond. According to the quantum molecular orbital theory of covalent bonding between atoms, electrons in molecules occupy molecular orbitals that are described, using quantum mechanical language, by a linear combination of... 

A second quantum mechanical bonding theory is molecular orbital theory. This theory is based on a wave description of electrons. The molecular orbital theory assumes that electrons are not associated with an individual atom but are associated with the entire molecule. Delocalized molecular electrons are not shared by two atoms as in the traditional covalent bond. For the hydrogen molecule, the molecular orbitals are formed by the addition of wave functions for each Is electron in each hydrogen atom. The addition leads to a bonding molecular... 

The trick is to make two equivalent orbitals in Be out of the atomic orbitals so that each hydrogen will see essentially the same electronic environment. We can accomplish this by mixing the 2s orbital and one of the empty 2p orbitals (say, the 2p ) to form two equivalent orbitals we call sp" hybrids, since they have both s and p characteristics. As with molecular orbital theory, we have to end up with the same number of orbitals we started with. The bonding lobes on the new spa and spb orbitals on Be are 180° apart, just as we need to form BeH2. In this manner, we can mix any type of orbitals we wish to come up with specific bond angles and numbers of equivalent orbitals. The most common combinations are sp, sp, and sp hybrids. In sp hybrids, one and one p orbital are mixed to get two sp orbitals, both of which... 

The basic concept of molecular orbital theory is that molecular orbitals may be constructed from a set of contributing atomic orbitals such that the molecular wave functions consist of linear combinations of atomic orbitals (LCAO).. in the case of the combination of two Is hydrogen atomic orbitals to give two molecular orbitals, the two linear combinations are written below so that atomic wave functions are represented by j/ and molecular wave functions by <)> ... 

Application of Molecular Orbital Theory to Catalysis Roger C. Baetzold The Stereochemistry of Hydrogenation of aj3-Unsaturated Ketones Robert L. Augustine Asymmetric Homogeneous Hydrogenation... 

The AMI (8) approximation to molecular orbital theory has been used for these studies. This method overcomes the problems that previous semiempirical methods (notably, MNDO) (9) have in describing hydrogen-bonds. It has been used with success in several hydrogen-bonding studies. (10-12) Ab initio studies of H-bonding systems are very sensitive to basis set and correction for electron-... 

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