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Pure Appl. Chem., Vol. 71, No. 10, pp. 1919-1981, 1999

Glossary of terms used in theoretical organic chemistry

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Open-shell systems - Atomic or molecular systems in which the electrons are not completely assigned to orbitals in pairs.

Orbital (Atomic or Molecular) - A wavefunction which depends explicitly on the spatial coordinates of only one electron.

Orbital correspondence analysis in maximum symmetry (OCAMS), method of - An extension of the correlation diagram procedure for determining reaction paths. The reactant(s) and product(s) are set up in their highest common symmetry point group. The preferred reaction path retains the symmetry of a subgroup in which all of the occupied molecular orbitals correlate across the diagram. Inclusion of the symmetry properties of the components of the spin-orbit coupling operator allows application of the method to thermal and photochemical reactions that do not conserve electron spin. HALEVI (1992).

Orbital interaction - Interaction of two orbitals due to their overlap which results in the formation of two new orbitals, one of which is lower in energy than the lowest energy level of the initial orbitals, while the energy level of another new orbital lies higher than the highest energy level of the initial orbitals. The notion may be extended to the interaction of several orbitals. In perturbation theory, the energy of the orbital interaction is proportional to the square of the overlap integral and inversely proportional to the energy difference between the interacting orbitals. ALBRIGHT, BURDETT, and WHANGBO (1985).

Orbital interaction diagram - A diagram which portrays in a qualitative or quantitative manner the splitting of the energy levels due to an orbital interaction.

Orbital isomers - Species distinguishable by different occupation of a set of available MOs. DEWAR, KIRSHNER and KOLLMAR (1974).

Overlap integral - The integral defining the summation over the space of the overlap of the electron density of two orbitals:
Smn = fmfndt.

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> Abstract
> General remarks
> Arrangement

> Fundamental physical constants used in the glossary
> References
> Appendix. Glossary of acronyms of terms used in theoretical organic chemistry

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