Oxidation of catechol to 2-hydroxymuconic semialdehyde

Singlet and triplet reaction pathways for the oxidation reaction of catechol to 2-hydroxymuconic semialdehyde were examined at the B3LYP/6-311G∗∗ level of theory for the uncatalyzed process. In three step mechanisms, the reactions proceed through a peroxy-like transition state, with initial oxygen attack at different carbon atom sites. The final product of the (open shell) singlet reaction is the semialdehyde that has been observed experimentally. The reaction barriers along the singlet surface are lower than those on the triplet pathway.