Fundamental and Overtone Vibrational Spectra of Gas-Phase Pyruvic Acid

Abstract

Pyruvic acid (CH(3)COCOOH) is an important keto acid present in the atmosphere. In this study, the vibrational spectroscopy of gas-phase pyruvic acid has been investigated with special emphasis on the overtone transitions of the OH-stretch, with Delta v(OH) = 2, 4, 5. Assignments were made to fundamental and combination bands in the mid-IR. The two lowest energy rotational conformers of pyruvic acid are clearly observed in the spectrum. The lowest energy conformer possesses an intramolecular hydrogen bond, while the next lowest rotational conformer does not. This difference is clearly seen in the spectra of the OH vibrational overtone transitions, and it is reflected in the anharmonicities of the OH-stretching modes for each conformer. The spectra of the OH-stretching vibration for both conformers were investigated to establish the effect of the hydrogen bond on frequency, intensity, and line width.

Gas-phase water-mediated equilibrium between methylglyoxal and its geminal diol

“…Our theoretical frequency puts the ν δ 13 at 3; 478 cm −1 , which is slightly red shifted compared to the experimental value of 3; 505 cm −1 . This discrepancy between the theoretically and experimentally derived frequencies is consistent with results from other studies (28,(32)(33)(34)(35). The ν δ 13 and ν δ 14 could also have a contribution from tetrol OH stretching vibrations which all fall near to those of MGD, making it difficult to distinguish or model them.…”

Gas-phase vibrational spectra of glyoxylic acid and its gem diol monohydrate. Implications for atmospheric chemistry

“…The calculated frequencies and integrated cross-sections are presented in Table 1 and Table 2. Previously, this method calculated the results of pyruvic acid and was in excellent agreement with experimental results and the results obtained with CCSD(T) methods [35,44].…”

“…A Bruker Tensor 27 with a permanent set-up of a globar, KBR beamsplitter, and MCT detector allowed for optimal mid-IR absorption spectroscopy. The set-up for this experiment has been described previously [31][32][33][34][35]. The glass cell has a path length of 75 cm.…”

Photochemistry of aqueous pyruvic acid

“…PA undergoes decarboxylation in the gas and aqueous phases by means of different mechanisms. Decarboxylation of gas phase PA has been seen to occur thermochemically, through IR multiphoton pyrolysis, as well as through UV and visible excitation (13,(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36). The main removal pathway of gas phase PA from the troposphere is UV photolysis, with reaction with OH radical providing a minor contribution (31).…”