Vibrational analysis and ab initio studies of propiolic acid



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Texas Tech University


A vibrational analysis and ab initio studies of propiolic acid have been carried out in a two part study. In the first part, infrared matrix isolation spectra of propiolic acid isolated in solid argon, carbon monoxide, nitrogen and neon at 11-35K have been recorded in the range 4000 - 400 cm^-1. Spectra were also recorded for the isotopically labeled O and H isotopomers isolated in argon and nitrogen matrices. Spectra have been interpreted using isotopic splitting patterns, correlations with spectra of related molecules, and MO normal coordinate analysis at the ab initio (6-31G* basis set) level and semi-emperical MINDO / 3 level using standard basis set.

Computational studies using MINDO / 3 and GAUSSIAN 82 have been carried out to determine geometries, energies, dipole moments, rotational constants, vibrational frequencies, force constants, and one-electron properties. Comparisons have been made with experimental data to check the accuracy of computed molecular parameters. Various unimolecular decomposition channels have been investigated and possible bimolecular decomposition channels postulated. The computed structures and energies of various intermediates have been determined. The internal rotation (torsional) barrier for hydroxyl group relative to the C-0 bond has been determined at various levels and the conversion from the cis to trans conformer has been identified as a prerequisite for some decomposition channels.



Vibrational spectra, Propionic acid