Chapter 1
Molecular Orbitals o Common Functional Groups


In this module, a broad and qualitative overview of basic molecular orbital (MO) theory is provided. The simplified picture of MO for some standard functional groups are emphasized. The concept of node in the context of MO and its effect on the energy levels of these MOs are also given.
The objective of this module is to provide important molecular orbitals of conjugated olefins, which are typically used in the discussion of cycloaddition and other pericyclic reactions. Understanding of orbital symmetry rules demands a prior knowledge of molecular oribtals.
In addition, molecular orbitals are very useful toward understanding reaction mechanism, such as the direction of approach of the nucleophiles, stereochemistry of elimination reactions and many more situations. Conformational features, stability of reactive intermediates etc., can also be explained by using molecular orbital theory concepts.