The given [4+4] cycloaddition process should be explained with the use of MO theory whether it occurs through thermal or photochemical pathway. Concept introduction: According to MO theory, In a molecule, the atomic orbitals of atoms constituted in the molecule are combined to produce new orbitals are called Molecular Orbitals . The numbers of MO’s are equals to the number of atomic orbitals are combined in such a way that the linear combination of similar atomic orbitals to form equal numbers of bonding and anti-bonding MO’s . The bonding MO’s are lower in energy than the anti-bonding MO’s. HOMO is the highest energized occupied orbital in the MO’s. LUMO is the lowest energized orbital in the MO’s. Frontier orbital theory says, In a cycloaddition reaction, the electron cloud flows from HOMO of the one molecule to LUMO of the other molecule. According to conservation of orbital symmetry , The phases of MO’s ( HOMO & LUMO ) of reactants must be symmetric in order to reaction occur. The thermal pathway of cycloaddition reaction occurs in the ground state of 1,3-butadiene. The photochemical pathway of cycloaddition reaction occurs in the excited state of 1,3-butadiene. To explain: the given [4+4] cycloaddition process with the use of MO theory whether it occurs through thermal or photochemical pathway.

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Chapter 16.8, Problem 19CC

Interpretation Introduction

Interpretation:

The given [4+4] cycloaddition process should be explained with the use of MO theory whether it occurs through thermal or photochemical pathway.

Concept introduction:

According to MO theory,

In a molecule, the atomic orbitals of atoms constituted in the molecule are combined to produce new orbitals are called Molecular Orbitals.

The numbers of MO’s are equals to the number of atomic orbitals are combined in such a way that the linear combination of similar atomic orbitals to form equal numbers of bonding and anti-bonding MO’s.

The bonding MO’s are lower in energy than the anti-bonding MO’s.

HOMO is the highest energized occupied orbital in the MO’s.

LUMO is the lowest energized orbital in the MO’s.

Frontier orbital theory says,

In a cycloaddition reaction, the electron cloud flows from HOMO of the one molecule to LUMO of the other molecule.

According to conservation of orbital symmetry,

The phases of MO’s (HOMO & LUMO) of reactants must be symmetric in order to reaction occur.

The thermal pathway of cycloaddition reaction occurs in the ground state of 1,3-butadiene.

The photochemical pathway of cycloaddition reaction occurs in the excited state of 1,3-butadiene.

To explain: the given [4+4] cycloaddition process with the use of MO theory whether it occurs through thermal or photochemical pathway.

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