What is a Photochemical reaction?
A chemical reaction that occurs by absorbing energy in the form of light or photons is called a photochemical reaction.
The photon energies lie mainly in the visible and U.V. region. Some photochemical reaction is as follow;
Photochemical Decomposition of Hydrogen Halides
\[\displaystyle 2HI\underset{{}}{\overset{{hv}}{\longrightarrow}}{{H}_{2}}+{{I}_{2}}\]
\[\displaystyle 2HBr\underset{{}}{\overset{{hv}}{\longrightarrow}}{{H}_{2}}+B{{r}_{2}}\]
Photochemical Decomposition of Ammonia
\[\displaystyle 2N{{H}_{3}}\underset{{}}{\overset{{hv}}{\longrightarrow}}{{N}_{2}}+3{{H}_{2}}\]
Photochemical Decomposition of Acetone
\[\displaystyle C{{H}_{3}}COC{{H}_{3}}\underset{{}}{\overset{{hv}}{\longrightarrow}}{{C}_{2}}{{H}_{6}}+CO\]
Photochemical combination of Hydrogen and Halogens to from Hydrogen Halides
\[\displaystyle {{H}_{2}}+{{X}_{2}}\underset{{}}{\overset{{hv}}{\longrightarrow}}2HX\]
Isomerization of Maleic acid to Fumaric acid
Dimerization of anthracene in benzene solution in the absence of oxygen
\[\displaystyle 2{{C}_{{14}}}{{H}_{{10}}}\underset{{}}{\overset{{hv}}{\longrightarrow}}{{C}_{{28}}}{{H}_{{20}}}\]
Cleavage reaction when they are suitably placed as, for example, in the following reaction
