Which of the following explicitly prevents highly substituted ortho-tetramethyl biphenyl systems fro — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

Biphenyl systems consist of two phenyl rings joined by a single bond. When massive substituents are placed at all four ortho positions, severe electrostatic repulsion (steric hindrance) occurs. To relieve this strain, the single bond rotates, powerfully locking the two rings into mutually perpendicular planes. Perpendicular planes strictly forbid Geometrical Isomerism, although they do enable Optical Isomerism.