Chapter 6: Isomerism in Organic Compounds and Drug Molecules: Chemistry and Significance in Biology

Molecules of organic compounds may have the same atomic composition but differ from each other based on either the way in which the atoms are connected or their special arrangement in space. Such variations are collectively called isomerism and include structural isomerism such as carbon chain, positional, and functional isomerism, and tautomerism. Molecular variation based on spatial arrangement is called stereoisomerism and includes geometrical (cis–trans or E–Z) and R–S (or optical) isomerism. In organic compounds and drug molecules, isomerism means variation not only in physical and chemical properties but also in biological effects. By using practical examples and problem-solving exercises, this chapter outlines the chemical basis and biological significance of isomerism.