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Content available remote Matrix isolation FTIR spectroscopical study of ethene secondary ozonide
A new method is used for the separation of ethene secondary ozonide (SOZ) from the other products of ethene ozonization reaction. The reaction was performed in the neat films of the reactants at 77 K. Ethene SOZ was separated from other products of the reaction by vacuum distillation at 190–210 K and analyzed by means of the matrix isolation IR absorption spectroscopy. Spectroscopic data from photolysis of the matrix isolated ozonide was used as an argument for assignment of the infrared spectral bands either to ethene SOZ or to other products of the reaction. The spectra of ethene SOZ isolated in the Ar matrix were analyzed by combining experimental results with the theoretical calculations performed at the MP2 6-311+G (3df, 3pd) level. A new assignment of some experimental fundamental bands is proposed taking in to account the Fermi resonance between CH stretch and the five membered ring vibrations. For the first time more than 30 weak infrared absorption bands were observed and assigned to various combination vibrations and overtones. By using new spectral information concerning the overtones and the combination bands it is concluded that the dissociation of unstable ethene SOZ involving breaking of any of the four CO bonds of the five membered ring of ethene SOZ has low probability. Dissociation of the ring starts from breaking of the OO bond. [...]
Methylglyoxal (MG) was studied by matrix-isolation IR spectroscopy supported by MP2/6-311++G(2d,2p) calculations. The experimental results show that the molecule exists in the trans conformation (Cs symmetry). The trans-MG isomer is estimated to lie 4.96 kcal/mol be low the cis-MG isomer and the rotational barrier is 5.48 kcal/mol on the ground-state path way from trans- to cis-MG. The spectra evidence formation of weak molecular MGźźźN2 complexes when the argon matrix is doped both with MG and N2.
The infrared absorption spectra of acetohydroxamic acid (CH3CONHOH) and its deuterated analogue (CH3CONDOD) isolated in argon and nitrogen matrices have been recorded for the first time. The infrared spectra prove that this molecule exists as the keto tautomer with intramolecular hydrogen bond in solid argon and nitrogen. Theoretical studies of the structure and spectral characteristics of the acetohydroxamic acid molecule, carried out on both MP2 and B3LYP levels with the 6-311++G(2d,2p) basis set, are in accordance with the experimental data.
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