Ja. Dobado et al., A COMPARATIVE MOLECULAR MECHANICS, SEMIEMPIRICAL AND AB-INITIO STUDY OF SATURATED 5-MEMBERED RINGS, Journal of molecular structure. Theochem, 109, 1994, pp. 205-212
The potential energy surfaces of five-membered homo- and heterocyclic
saturated rings (cyclopentane, tetrahydrofuran, tetrahydrothiophene, p
yrrolidine and N-methylpyrrolidine) have been studied using molecular
mechanics, semiempirical (MNDO, AM1 and PM3) and ab initio methods (HF
/6-31G*) to determine the ability of each in describing the geometry
and stability of each of the mentioned compounds. The molecular mechan
ics and ab initio calculations are consistent in the relative energies
and geometries determined for the conformers of all ring systems, whe
reas the semiempirical calculations yield flatter geometries and scatt
ered energies. The PM3 method produces the best results among the semi
empirical methods tested.