Chair conformation : Stability :: Boat conformation : ?

The chair form of cyclohexane is the most stable because every carbon is sp³ hybridized and the bonds are almost all ideal tetrahedral angles, giving minimal angle strain and no steric clashes. In contrast, the boat form forces many carbons to adopt angles that are far from 109. 5°, creating angle strain, and the two “flagpole” hydrogens clash, adding steric strain. Therefore, the boat conformation is intrinsically less stable and is often called an unstable or strained conformation. For example, when a cyclohexane ring flips from chair to boat, the energy increases by about 5–8 kcal/mol, showing the boat’s instability.