angle strain

In chemistry, angle strain refers to the instability that arises when the bond angles within a molecule deviate from their ideal values. This concept was central to Adolf von Baeyer's strain theory, proposed in 1885.12

Baeyer suggested that the stability of cyclic compounds depends on how much their bond angles differ from the ideal tetrahedral angle of 109°28'. For instance, in cyclopropane, the three carbon atoms form a triangle with 60° bond angles. This significant deviation from the ideal angle creates considerable strain, making cyclopropane relatively unstable and reactive. Similarly, cyclobutane experiences angle strain, though less than cyclopropane. Larger rings, like cyclohexane, can adopt non-planar conformations (e.g., chair and boat shapes) to relieve this strain, making them more stable.1234