In Chemistry, What Is a Molecular Orbital?

Molecular orbitals ^[1] (MO) can be combined linearly with atomic orbitals. It can be formed by linear combination of corresponding atomic orbits. Several atomic orbitals combine to form several molecular orbitals. Among the molecular orbitals generated by combination, those with lower energy than atomic orbitals are called bonding orbitals; those with higher energy than atomic orbitals are called anti-bond orbitals; those with no corresponding atomic orbitals with similar energy (similar energy and symmetrical matching) are called Non-key tracks. Molecular Orbital (MO) was originally proposed by Mulliken and Hund. After Huckel (simple molecular orbital theory, HMO), Roothaan (self-consistent field molecular orbital theory), Fukui Kenichi (frontline molecular orbital theory, abbreviated FMO), Woodward and Hoffmann (conservation of molecular orbital symmetry) and other scientists continue to explore and form a set of mature theories, which solve the molecular structure problems like the valence bond theory (VB) and coordination field theory (LF).

Molecular Orbital (MO) was originally proposed by Mulliken and Hund. After Huckel (simple molecular orbital theory, HMO), Roothaan (self-consistent field molecular orbital theory), Fukui Kenichi (frontline molecular orbital theory, abbreviated FMO), Woodward and Hoffmann (conservation of molecular orbital symmetry) and other scientists continue to explore and form a set of mature theories, which solve the molecular structure problem in the same way as valence bond theory (VB) and coordination field theory (LF).

After half a century of rapid development, molecular orbital theory has become the mainstream of contemporary chemical bond theory. Nowadays, it is mostly used for the study of the properties of conjugated molecules, quantum chemistry, the chemical activity of molecules and the interaction between molecules, the study of elementary chemical reactions, and the guidance of the synthesis of certain complex organic compounds.

The birth of molecular orbital theory

In 1926-1932, when discussing the spectrum of molecules (especially diatomic molecules), Mulliken ^[2]

Molecular orbits (MO) can be combined linearly with atomic orbits ^[8]

Molecular motion description

The electrons in a molecule move across the entire range of molecules, and the state of movement of each electron can use one molecule

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Today, the front-line orbital theory is still being further developed, and its application range is also expanding. At present, more research is focused on various radical reactions, polymerization reactions, electronic structures of inorganic substances and complexes, etc .; there are also a large number of studies on compounds containing NN, NS, C-Si, S-Cl, hydrogen bonds and other structures. ^[8] .

Regarding molecular orbitals, I think the future development direction will guide the synthesis of some complex organic compounds. Many groups with specific functions do not work well on existing compounds, and it is not possible to use them because of their toxicity. Therefore, these specific groups are linked to some substrates that are conducive to their function to make them function. But today many compounds cannot be linked for many reasons. I think that the related knowledge in molecular orbitals can be used in the future to make it easier to connect and form complex polymers with better functionality.