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Title: | Conformational Analysis and Near-Infrared-Induced Rotamerization of Malonic Acid in an Argon Matrix | Authors: | Maçôas, Ermelinda M. S. Fausto, Rui Lundell, Jan Pettersson, Mika Khriachtchev, Leonid Räsänen, Markku |
Issue Date: | 21-Dec-2000 | Publisher: | American Chemical Society | Citation: | The Journal of Physical Chemistry A. 104:50 (2000) 11725-11732 | Abstract: | Relative energies and vibrational spectra of the conformational states of a malonic acid monomer (HOOCCH2COOH) were calculated using various levels of approximation [Hartree−Fock (HF), Møller−Plesset to second order (MP2), and B3LYP density functional theory (DFT)]. The calculations predict the existence of six different conformers according to skeletal C−C bond and O−H bond rotation. Three conformers are found with energies close enough to enable their spectroscopic observation. The lowest-energy conformer (I) shows a nearly planar structure with an OH···OC intramolecular hydrogen bond closing a six-member ring. The second- and third-lower energy conformers (II and III) differ from the conformational ground state by less than 5 kJ mol-1. Conformers II and III adopt a cis arrangement around the C−O bonds: conformer II exhibits the two carbonyl bonds in a nearly orthogonal arrangement, with one carboxylic group in the plane containing the carbon atoms, whereas in conformer III (C2 symmetry), the carbonyl bonds make a dihedral angle of ca. 120°, and both carboxylic groups are placed out of the plane containing the skeletal carbons. Their relative energy is predicted by the highest-level calculations to be ca. 1 kJ mol-1. The theoretical predictions agree with the analysis of the infrared spectra of monomeric malonic acid isolated in a solid argon matrix, where the presence of the three above-mentioned conformers was unequivocally identified. Narrowband tunable irradiation in the near-infrared region was found to promote efficiently the interconversion between the experimentally observed conformers. | URI: | https://hdl.handle.net/10316/10675 | ISSN: | 1089-5639 | DOI: | 10.1021/jp002853j | Rights: | openAccess |
Appears in Collections: | FCTUC Química - Artigos em Revistas Internacionais |
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