Molecular Structures, Electronic Properties, and Energetics of Fluorinated Allenes and Isomeric Acetylenes

Article abstract of DOI:10.1021/j100360a010

The geometries, energies, and various electronic properties of the allenes CH2=C=CH2, CH2=C=CHF, CHF=C=CHF, CH2=C=CF2, CHF=C=CF2, CF2=C=CF2, and the acetylenes CH3C<*>CH, CH3C<*>CF, CF3C<*>CH, and CF3C<*>CF have been calculated at the SCF level with a double-ξ basis set augmented by polarization functions on carbon.Final energies and properties were calculated with a fully polarized double-ξ basis set.Final energies were determined at the MP-2 level.The C=C and C-F bond lengths in the allenes decrease with increasing fluorine substitution.The CCC bond angles in CH2=C=CHF, CHF=C=CHF, and CHF=C=CF2 all deviate about 1 deg from collinearity.A series of isodesmic reaction enthalpies was calculated to derive heats of formation of all the fluorinated allenes and acetylenes and to evaluate their isodesmic stabilities.The effects of fluorination on the thermodynamic stabilities of allenes, acetylenes, and ethylenes are compared.Mulliken charge distributions, dipole moments, and ionization potentials were calculated for each molecule.The properties of the HOMO and LUMO's in the various fluorinated allenes and acetylenes are discussed.