Hydrogen atoms, reactions with oxygen Subject

The comments made about the diradical hypothesis with respect to the photochemistry of cyclopentanone are equally applicable to cyclohexanone. Since the formation of none of the products listed in reactions 15-18, and (15,29) is quenched by even 10-20 mm. of oxygen the existence of diradical intermediates in this system is subject to question. The alternative mechanism would be one that causes a concerted split of the ketone molecule in the excited state into two (in the cases of reactions 15 and 16) or three (reaction 17) molecular fragments. Both 16 and 17 are analogous to reactions 3 and 2 in the photochemistry of cyclopentanone and do not involve a shift of hydrogen atom from one... 

Degradation of polyolefins such as polyethylene, polypropylene, polybutylene, and polybutadiene promoted by metals and other pro-oxidants occurs via a combination photo-oxidative mechanism. A general mechanism common to all these reactions is that shown below. The reactant radical may be produced by any suitable mechanism from the interaction of air/oxygen wdth polyolefins (Scott, 1964 Sipinen et al, 1993) to form peroxides which subsequently decompose by the action ultraviolet radiation. These decomposition intermediates may undergo many reactions such as abstraction of hydrogen atoms from the pol) mer until the backbone ultimately converted into a polymer with ketone functionalities which is degraded by a Norrish mechanism discussed above. A recent review by Scott (1995) elegantly discusses this subject. 

The anodic oxidation of methanol was considered as one of the most interesting subjects in electrochemistry during the last 15 years. Besides very characteristic reaction pathways and electrocatalytic effects, the methanol molecule with its four hydrogen atoms is the basis of a high-energy density liquid fuel. The reaction of methanol with oxygen follows the chemical route... 

---