Photodegradation

Commonly, the term is used loosely to refer to the combined action of sunlight and air, which cause oxidation and hydrolysis.

In the case of beer, UV radiation causes a process that entails the degradation of hop bitter compounds to 3-methyl-2-buten-1-thiol and therefore changes the taste.

Pesticides are however selected in part not to photodegrade readily in sunlight in order to allow them to exert their biocidal activity.

Thus, more modalities are implemented to enhance their photodegradation, including the use of photosensitizers, photocatalysts (e.g., titanium dioxide), and the addition of reagents such as hydrogen peroxide that would generate hydroxyl radicals that would attack the pesticides.

They have deleterious effects on aquatic organisms including toxicity, endocrine disruption, genetic damage.

Iodine (in the form of Lugol's solution) and colloidal silver are universally used in packaging that lets through very little UV light so as to avoid degradation.

Ultraviolet rays interact with these bonds to form free radicals, which then react further with oxygen in the atmosphere, producing carbonyl groups in the main chain.

Many organic chemicals are thermodynamically unstable in the presence of oxygen; however, their rate of spontaneous oxidation is slow at room temperature.

[3] Photochemical reactions are initiated by the absorption of a photon, typically in the wavelength range 290–700 nm (at the surface of the Earth).