Stereoisomerism

Stereoisomers are, by definition, isomers that share IDENTICAL bond connectivity -- exactly the same atoms bonded to exactly the same other atoms -- and differ only in how their groups or atoms are arranged in three-dimensional SPACE. The branch of chemistry devoted to studying this spatial (three-dimensional) side of molecular structure is called stereochemistry, and it is far from a purely academic concern: stereoisomers show up constantly in living systems, since metabolic pathways, natural-product biosynthesis and drug actio …