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 $H-C\equiv N$ and $H-N\equiv C$ perfectly illustrates a diad system.