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Experimental and Computational Studies on the Gas-Phase Acidity of 5,5-Dialkyl Barbituric Acids.

ABSTRACT: The gas phase acidities (GA) of 5,5-alkylbarbituric acids have been experimentally determined by electrospray ionization-triple quadrupole (ESI-TQ) mass spectrometry and by using the extended kinetic Cooks method (EKCM). The GAs of C-H (1330.9 ± 10.0 kJ mol^-1) and N-H (1361.5 ± 10.5 kJ mol^-1) deprotonated sites of bifunctional barbituric acid were determined from the selective production of their corresponding heterodimers. The GA value in the N-H site was confirmed by measuring the GAs of 5,5-dimethyl- and 5,5-diethyl barbituric acids (∼1368 kJ mol^-1). The experimental results have been rationalized and discussed with the support of quantum chemical calculations with Gaussian-n (G3 and G4) composite methods, which confirmed the excellent consistency of the results.

SUBMITTER: Davalos-Prado JZ

PROVIDER: S-EPMC8495898 | biostudies-literature | 2021 Aug

REPOSITORIES: biostudies-literature

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Experimental and Computational Studies on the Gas-Phase Acidity of 5,5-Dialkyl Barbituric Acids.

Dávalos-Prado Juan Z JZ González Javier J Oliva-Enrich Josep M JM Urrunaga Emma J EJ Lago Alexsandre F AF

Journal of the American Society for Mass Spectrometry 20210625 8

The gas phase acidities (GA) of 5,5-alkylbarbituric acids have been experimentally determined by electrospray ionization-triple quadrupole (ESI-TQ) mass spectrometry and by using the extended kinetic Cooks method (EKCM). The GAs of C-H (1330.9 ± 10.0 kJ mol<sup>-1</sup>) and N-H (1361.5 ± 10.5 kJ mol<sup>-1</sup>) deprotonated sites of bifunctional barbituric acid were determined from the selective production of their corresponding heterodimers. The GA value in the N-H site was confirmed by meas ...[more]

PMID: 34170704

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