A Photochemical Reaction and Applications in Organic Synthesis

Abstract

Chemical as well as physical property that may occur under the influence of light is called Photochemistry. Photochemical transformations have been governed by two fundamental principles. These principals are First law: This law is also called as Grotthuss-Draper law; it states that for a photochemical reaction to take place it should be essential that light must be absorbed by a compound. Second law: The second law or Stark-Einstein law gives a photo equivalence law which is states that for each photon of light absorbed by a compound only one molecule of compound is activated for corresponding reaction. The efficiency of each photochemical process is calculated by Quantum Yield (Φ). Many photochemical reactions are complex, thus the quantum yield is specified for a particular event. It is defined as “ratios of the number of moles of a reactant disappearing, or the number of moles of a product obtained, per one mole of light absorbed by compound.” After that many of secondary reactions proceeded (shown in the gray box). Absorption of light (uv/vis) induces energy sufficient in molecule to break covalent bonds. Since, E = hc / λ, hence, longer wavelength have less energy and vice-versa. Consequently, ultraviolet light is most effect photochemical reactions. In this review we discuss about amongst all some of photochemical reactions collectively which are initiated by ultraviolet light specifically.