The photochemistry of benzene involves the absorption of ultraviolet UV light, which leads to the excitation of electrons in the benzene molecule and the formation of reactive intermediates. The mechanism can be divided into several steps:1. Absorption of UV light: When benzene is exposed to UV light, it absorbs the energy and promotes an electron from its highest occupied molecular orbital HOMO to the lowest unoccupied molecular orbital LUMO . This process creates an excited state of the benzene molecule, which is highly reactive.2. Formation of reactive intermediates: The excited benzene molecule can undergo various reactions, depending on the specific conditions. One possible pathway is the formation of a singlet diradical intermediate, where two carbon atoms in the benzene ring have unpaired electrons. This diradical can then undergo intersystem crossing to form a more stable triplet diradical.3. Reaction with molecular oxygen: The triplet diradical can react with molecular oxygen O2 to form a peroxyl radical intermediate. This reaction involves the addition of an oxygen molecule across one of the carbon-carbon double bonds in the benzene ring.4. Formation of phenol: The peroxyl radical intermediate can undergo a series of reactions, including hydrogen atom abstraction from another benzene molecule or another suitable hydrogen donor. This process results in the formation of a hydroperoxide intermediate, which can then undergo a rearrangement reaction to form phenol and a hydroxyl radical.5. Termination: The hydroxyl radical can react with another radical species, such as the peroxyl radical, to form stable products and terminate the reaction.In summary, the photochemistry of benzene involves the absorption of UV light, formation of reactive diradical intermediates, reaction with molecular oxygen, and a series of reactions that ultimately lead to the formation of phenol. This process highlights the importance of light-induced reactions in the transformation of organic compounds and the generation of new products.