AN INVESTIGATION OF STRUCTURAL STABILITY AND INTERNAL-ROTATION IN 3-CYCLOPROPENECARBOXALDEHYDE AND 3-CYCLOPROPENECARBOXYLIC ACID FLUORIDE BY AB-INITIO CALCULATIONS

The structural stability and internal rotation in 3-cyclopropenecarbox aldehyde and 3-cyclopropenecarboxylic acid fluoride were investigated by ab initio calculations with a 6-31G atomic basis in the latter and a 6-311G atomic basis set in the former case. For the sake of compar ison also results obtained with a 3-21G basis are given in the paper. As expected, it turned out that this basis set is not large enough for three-membered rings. The calculations were carried out both at the R estricted Hartree-Fock (HF) and the second order Moller-Plesset (MP2) levels. The trans-form is predicted to be the lower energy conformer f or both molecules. However, in case of the fluoride the two conformers have nearly the same energy. Full optimization was performed at the t ransition states and the asymmetric potential function for the CXO int ernal rotations was predicted for both molecules.