![relative energies of atomic orbitals relative energies of atomic orbitals](https://i.ytimg.com/vi/EwnU8RalZOw/maxresdefault.jpg)
Our picture of the degree of double bond character between adjacent carbon atoms in a polyene is based on whether the various contributing molecular orbitals are bonding or antibonding. In a neutral polyene, all of the π electrons are in the bonding molecular orbitals. The energies of the molecular orbitals increase as the number of nodal planes increases.Ī group of molecular orbitals for a polyene can be separated into a group of bonding molecular orbitals (corresponding to the number of double bonds) and an equal number of antibonding molecular orbitals. The bonding molecular orbital of ethene is symmetric the anti-bonding molecular orbital of ethene is antisymmetric with respect to a nodal plane. The electron density at this nodal plane is zero. Molecular orbitals may be symmetric or antisymmetric based on the sign of the molecular orbital at one point compared to a related point on the other side of a nodal plane. Subtracting the equations for the wave functions of atomic orbitals with opposite signs gives destructive overlap and produces an antibonding molecular orbital. This combination gives rise to bonding molecular orbitals. Adding orbitals with the proper sign of the wave function corresponds to constructive overlap of atomic orbitals. We obtain these orbitals by adding or subtracting the equations that describe the energies of atomic orbitals. Molecular orbitals are made from linear combinations of atomic orbitals. David Rawn, in Organic Chemistry Study Guide, 2015 11.3 Molecular orbital Models of conjugated systems