Jf. Liebman et al., Computational study of ring strain in 1,3,2-dioxathiolane, its 2-oxide andits 2,2-dioxide, ACT CHEM SC, 53(11), 1999, pp. 1003-1008
The strain energies in the five-membered rings 1,3,2-dioxathiolane (1), its
2-oxide (2) and 2,2-dioxide (3) have been evaluated using B3LYP and QCISD(
T)//MP2 calculations and the standard 6-31G* basis set. Two different model
s have been used, one based on an isodesmic reaction involving methane and
ethane, and one applying the chair-form of cyclohexane as a strain-free ref
erence. Thermally corrected strain energies obtained by B3LYP and with cycl
ohexane as a reference are 10.1, -1.3 and 5.8 kcal mol(-1) for 1, 2 and 3,
respectively. The corresponding values obtained by QCI calculations are 8.1
, -2.1 and 4.4 kcal mol(-1), respectively. The negative value for 2 is inte
rpreted in terms of absence of destabilizing interactions present in 1 and
3.