The author is a Professor of Organic Chemistry at Bangalore University, Bangalore. His main area of research is organosilicon chemistry with particular attention to developing new synthetic procedures and reagents, and studying the reaction mechanisms.

In the first part of the article, thermal solvent-free reactions were described. In this part solvent-free reactions brought about by light radiation are discussed.

Solid–state Photochemical Reactions

The transformation of one compound into another is a consequence of bond-breaking and bond-forming process either within the molecule (intramolecular) or between molecules (intermolecular), and is brought about thermally or photochemically. The functional group in a reactant molecule absorbs appropriate electronic energy whereby the molecule attains the excited state and forms products. The molecules that absorb light in the UV-visible range, that is, the molecules that undergo p–p* and n–p* electronic transitions, can in principle react when exposed to radiation of right frequency. Olefins, ketones, a,b-unsaturated carbonyl compounds, carboxylic acids and derivatives, aromatic compounds and dienes are some of the widely studied organic compound classes that undergo photochemical reactions. It should also be noted that the process vital to the occurrence and continuation of life on earth is a complex sequence of photochemical reactions called photosynthesis.

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Address for Correspondence

Gopalpur Nagendrappa
Department of Chemistry
Bangalore University
(Central College Campus)
Bangalore 560001, India.