Which of the following chemical systems serves as a classic example of a "Diad" tautomeric system? — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

Tautomerism involves the rapid oscillation of a mobile atom between polyvalent atoms. In a Diad system, the hydrogen atom migrates strictly between two adjacent atoms (a 1,2-shift). The interconversion of Hydrogen Cyanide ($H-C\equiv N$) and Hydrogen Isocyanide ($H-N\equiv C$) perfectly illustrates a diad system, as the proton shifts directly from carbon to the adjacent nitrogen.