Introduction:
Sachse and Mohr Theory expanded on the idea of non-planar conformations by proposing a theory specifically for cyclohexane and larger rings. This theory is also known as the Theory of Stainless Rings.
Key Concepts of Sachse-Mohr Theory:
Chair Conformation: Sachse and Mohr proposed that cyclohexane adopts a chair conformation, where all bond angles are 109.5°, eliminating angle strain completely.
Puckered Rings: For cycloalkanes larger than cyclohexane, they proposed that the rings can adopt puckered conformations that avoid strain, similar to the chair form in cyclohexane.
Stability Explanation:
Cyclohexane: The chair conformation of cyclohexane is strain-free because it allows all carbon atoms to achieve the ideal bond angles of 109.5° and minimizes steric interactions.
Larger Rings: For rings with more than six carbon atoms, puckered or twisted conformations are favored, which prevent angle strain and make the rings stable despite their larger size.
Advantages Over Baeyer’s Theory:
Applicability to Larger Rings: Unlike Baeyer’s theory, which failed for larger rings, Sachse-Mohr's theory can explain the stability of these rings due to their ability to adopt strain-free conformations.
Conformational Flexibility: It also accounts for the conformational flexibility of cycloalkanes, providing a more accurate description of their structures and stabilities.