What does a "0" inside a bicyclo bracket (e.g., Bicyclo[4.4.0]decane) indicate about the structure? — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

A zero-carbon bridge implies there are no intermediate carbons between the two bridgeheads on that path. They share an adjacent bond directly, which is the definition of a fused alicyclic system.