1.3- Dioxolanes ring-strain energies

Calculation of group increments for oxygen, sulfur and nitrogen compounds has allowed the estimation of conventional ring-strain energies (CRSE) for saturated heterocycles from enthalpies of formation. For 1,3-dioxolane, CRSE is about 20 kJ mol . In 2,4-dialkyl-l,3-dioxolanes the cis form is always thermodynamically the more stable by approximately 1 kJ mol" . 

As mentioned before, the AHg, value for the polymerization of 6,8-dioxabicyclo [3.2.1] octane is less negative than that for l,3-dioxolanes. Bicyclo [3.2.1] octane, in which a five-membered ring is fused to a cyclohexane ring at two axial positions, has 51 kJ/mol strain energy. However, from the fact that 7-oxabicyclo [2.2.1] heptane has less strain energy than bicyclo [2.2.1] heptane can be deduced that the strain energy of 6,8-dioxabicydo [3.2.1] octane may also be less than that of bicyclo [3.2.1] octane. 

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