isosterismthe
Isosterism is a principle in chemistry describing the replacement of atoms or groups with others that have similar electronic structure and size, resulting in similar physical properties and reactivity. The concept, developed in the mid-20th century by Irving Langmuir and colleagues, seeks to explain why different substituents can produce analogous behavior in molecules and crystals. In practice, isosteres are fragments with the same number of valence electrons and similar steric demands, so that the overall shape and electron distribution of the molecule are preserved.
Classical isosteres refer to replacements among elements in the same main group that closely match in size
Examples include replacing carboxyl groups with tetrazole rings to mimic acidity and charge distribution. Isosterism guides