Photodissociation, also known as photolysis, is the process by which a molecule absorbs a photon of light and breaks down into smaller fragments. The mechanism of photodissociation of benzene and cyclohexane in the presence of ultraviolet UV light differ due to their distinct molecular structures and electronic configurations.Benzene C6H6 is an aromatic compound with a planar hexagonal ring structure and delocalized -electrons. When benzene absorbs UV light, it undergoes electronic excitation, promoting one of its -electrons to a higher energy level. This process results in the formation of an excited singlet state, which can then undergo intersystem crossing to form a triplet state. In the triplet state, one of the -electrons is more loosely bound to the molecule, making it more susceptible to dissociation.The photodissociation of benzene typically occurs through a homolytic cleavage of one of the carbon-carbon C-C bonds in the ring, generating two highly reactive phenyl radicals. These radicals can then undergo further reactions, such as recombination or reaction with other molecules.Cyclohexane C6H12 , on the other hand, is a non-aromatic, saturated hydrocarbon with a chair conformation and no delocalized -electrons. When cyclohexane absorbs UV light, it also undergoes electronic excitation, but the process is different from that of benzene. In cyclohexane, one of the -bonds between carbon and hydrogen C-H is excited to a higher energy level, leading to the formation of an excited singlet state.The photodissociation of cyclohexane typically occurs through the homolytic cleavage of one of the C-H bonds, generating a hydrogen radical and a cyclohexyl radical. These radicals can then undergo further reactions, such as recombination or reaction with other molecules.In summary, the main differences between the photodissociation mechanisms of benzene and cyclohexane in the presence of UV light are:1. Benzene undergoes electronic excitation of its delocalized -electrons, while cyclohexane undergoes excitation of its localized -bonds.2. Benzene dissociates through the cleavage of a C-C bond in the aromatic ring, while cyclohexane dissociates through the cleavage of a C-H bond.3. The resulting radicals from benzene photodissociation are phenyl radicals, while those from cyclohexane photodissociation are cyclohexyl radicals and hydrogen radicals.