Structures and Stabilities of C3H3- Anions: an ab initio Molecular Orbital StudyReport as inadecuate

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Croatica Chemica Acta, Vol.61 No.4 December 1988. -

The various minima and some of the saddle points on the

C3H3- potential energy surface have been studied with ab initio

molecular orbital calculations. The structures of these species have

been determined by full geometry optimizations at the Hartree-

-Fock level with the diffuse-function augmented basis sets 3-21+G and 6-31+G*. In addition, improved energy compairsons have been obtained at the MP3-6-31 + + G** level, and vibrational frequency analysis of the various species have been carried out in order to characterize the stationary points as well as to determine zero-point vibrational energies of these species. Eight stable species have been found on the potential energy surface of C3H3-. In descending order of stability, they are: l-propynyl 1, allenide 3, cyclopropen-l-ide 5, prop-2-en-l-yliden- I-ide 6, three isomers EZ, EE, ZZ of prop-l-en-3-yliden-l-ide 7, 8, 9 and cyclopropen-3-ide 10 ions. The transition structures found are those for the methyl migration of 1, the inversion at the anionic center of 3, and the pseudorotation of 10.

In addition, for all the equilibrium structures found, the electron

affinities of the corresponding free radicals have been calculated.

From these results, it is deduced that, among the eight anionic equilibrium structures, only 10 is unstable toward spontaneous

electron loss.

Author: Wai-Kee Li - ; The Chinese University of Hong Kong, Shatin, N. T., Hong Kong



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