Photochemistry

Photochemistry is crucial in nature since it is the core of photosynthesis, vision, and the creation of vitamin D from sunshine. Temperature-driven reactions are not the same as photochemical reactions. Photochemical pathways get access to high-energy intermediates that cannot be formed thermally, allowing reactions that would otherwise be inaccessible via thermal processes to overcome enormous activation barriers in a short period of time. The photo degradation of plastics shows how damaging photochemistry can be. As defined by the Woodward–Hoffmann process theory, the absorption of a photon of light by a reactant molecule may allow a reaction to occur not only by bringing the molecule to the required activation energy but also by changing the symmetry of the molecule's electronic configuration, allowing an otherwise inaccessible reaction path. One example of a per cyclic reaction that may be examined using these rules or the associated frontier molecular orbital theory is a 2+2 cycloaddition reaction. Photochemical reactions can be hundreds of times faster than thermal reactions; reactions as fast as 109 seconds and associated processes as fast as 1015 seconds have been reported. The majority of photochemical changes take place in a set of basic phases called main photochemical processes. The excited-state proton transfer is a common example of these processes!