What is the theoretical minimum number of consecutive (adjacent) double bonds strictly required for — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

In cumulative diene systems, an even number of consecutive double bonds (e.g., 2 in allenes) forces the terminal $sp^2$ carbon substituents into mutually perpendicular planes, preventing GI. An odd number of consecutive double bonds (e.g., 3 in a butatriene skeleton) ensures the terminal carbon substituents reside exactly in the same plane, successfully fulfilling the geometric requirement for cis/trans isomerism.