7.1: Ring Strain and the Structure of Cycloalkanes Stable cycloalkanes cannot be formed with carbon chains of just any length. Recall that in alkanes, carbon adopts the tetrahedral geometry in which the angles between bonds are 109.5°. For some cycloalkanes to form, the angle between bonds must deviate from this ideal angle, an effect known as angle strain. Additionally, some hydrogen atoms may come into closer proximity with each other than is desirable, an effect called torsional strain. These destabilizing effects are known as ring strain. 7.2: Cycloalkanes and Ring Strain For cyclic alkanes, only partial rotation of carbon-carbon single bonds can occur. The actual shape of the carbon ring distorts from the traditional geometric shapes to reduce steric hindrance and ring strain to lower the overall potential energy of the molecule. 7.3: Cyclohexane Conformations Cyclohexane rings are notably stable. Understanding the conformations of cyclohexane and their relative energies is helpful when studying the chemistry of simple carbohydrates (monosaccharides). 7.4: Conformations of Monosubstituted Cyclohexanes For monosubstituted cyclohexanes, the axial or equatorial orientation of the substituent influences the overall potential energy of the conformation. 7.5: Conformations of Disubstituted Cyclohexanes Because six-membered rings are so common among natural and synthetic compounds and its conformational features are rather well understood, we shall focus on the six-membered cyclohexane ring to study the energetic relationship of conformation and overall potential energy. 7.6: Polycyclic Alkanes 7.7: Carbocyclic Products in Nature 7.8: Steroids The important class of lipids called steroids are actually metabolic derivatives of terpenes, but they are customarily treated as a separate group. Steroids may be recognized by their tetracyclic skeleton, consisting of three fused six-membered and one five-membered ring.