Photochemistry
1.1 Introduction:- Photochemistry is concerned with reactions which
are initiated by electronically excited molecules. Such molecules are
produced by the absorption of suitable radiation in the visible and near
ultraviolet region of the spectrum. Photochemistry is basic to the world
we live in with sun as the central figure, the origin of life must have
been a photochemical act. Simple gaseous molecules like methane,
ammonia and carbon dioxide must have reacted photochemically to
synthesize complex organic molecules like proteins and nucleic acids.
Photobiology, the photochemistry of biological reactions, is a rapidly
developing subject and helps in understanding the phenomenon of
photosynthesis, phototaxin, photoperiodism, vision and mutagenic
effects of light.
The relevance of photochemistry also lies in its varied
applications in science and technology. Synthetic organic
photochemistry has provided methods for the manufacture of many
chemicals which could not be produced by dark reactions. Some
industrially viable photochemical syntheses include synthesis of
vitamin D2 from ergosterol isolated from yeast, synthesis of
caprolactum which is the monomer for Nylon 6, manufacture of
cleaning solvents and synthesis of some antioxidants.
Photoinitiated polymerization and photopolymerisation are used
in photography, lithoprinting and manufacture of printed circuits for
the electronic industry.
The photophysical phenomena of flourescence and
phosphorescence have found varied applications in fluorescent tube
