Isosterics

Part of speech: noun

Definitions

1. The study of structures or molecules that have similar shapes or volumes despite differences in composition ; the concept of chemical groups or atoms exhibiting comparable spatial and electronic characteristics ; the analysis of substituents or fragments in compounds that possess equivalent steric effects and geometric properties
2. Investigation of molecular entities with alike three-dimensional forms despite varied chemical makeup ; the examination of functional groups or atoms sharing similar sizes and shapes ; the consideration of components in chemical structures that cause parallel spatial hindrance and shape features
3. Exploration of chemical species exhibiting analogous spatial arrangements regardless of differing constituents ; the assessment of substituents or atomic groups with comparable volume and shape ; the evaluation of elements in molecules that produce equivalent steric influence and geometric similarity

Etymology: Irving Langmuir, the American chemist, coined "isostere" to describe molecules that share the same number of atoms and the same number of valence electrons, such as nitrogen and carbon monoxide. The name combines Greek "isos," meaning equal, with "stereos," meaning solid, so the term originally pointed to equal solidity or bulk rather than to exact shape. The noun "isosterics" follows the pattern of fields ending in "-ics," such as physics or mechanics, and names the study of such equivalences. Its meaning has widened over time: chemists now apply "isosteric" to groups of atoms or substituents that occupy similar space or have similar electronic character, even when their composition differs.