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Ventura ON, Segovia M, Vega-Teijido M, Katz A, Kieninger M, Tasinato N, Salta Z. Correcting the Experimental Enthalpies of Formation of Some Members of the Biologically Significant Sulfenic Acids Family. J Phys Chem A 2022; 126:6091-6109. [PMID: 36044372 DOI: 10.1021/acs.jpca.2c04235] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sulfenic acids are important intermediates in the oxidation of cysteine thiol groups in proteins by reactive oxygen species. The mechanism is influenced heavily by the presence of polar groups, other thiol groups, and solvent, all of which determines the need to compute precisely the energies involved in the process. Surprisingly, very scarce experimental information exists about a very basic property of sulfenic acids, the enthalpies of formation. In this Article, we use high level quantum chemical methods to derive the enthalpy of formation at 298.15 K of methane-, ethene-, ethyne-, and benzenesulfenic acids, the only ones for which some experimental information exists. The methods employed were tested against well-known experimental data of related species and extensive CCSD(T) calculations. Our best results consistently point out to a much lower enthalpy of formation of methanesulfenic acid, CH3SOH (ΔfH0(298.15K) = -35.1 ± 0.4 kcal mol-1), than the one reported in the NIST thermochemical data tables. The enthalpies of formation derived for ethynesulfenic acid, HC≡CSOH, +32.9 ± 1.0 kcal/mol, and benzenesulfenic acid, C6H5SOH, -2.6 ± 0.6 kcal mol-1, also differ markedly from the experimental values, while the enthalpy of formation of ethenesulfenic acid CH2CHSOH, not available experimentally, was calculated as -11.2 ± 0.7 kcal mol-1.
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Affiliation(s)
- Oscar N Ventura
- Computational Chemistry and Biology Group, CCBG, DETEMA, Facultad de Química, Universidad de la República, 11400 Montevideo, Uruguay
| | - Marc Segovia
- Computational Chemistry and Biology Group, CCBG, DETEMA, Facultad de Química, Universidad de la República, 11400 Montevideo, Uruguay
| | - Mauricio Vega-Teijido
- Computational Chemistry and Biology Group, CCBG, DETEMA, Facultad de Química, Universidad de la República, 11400 Montevideo, Uruguay
| | - Aline Katz
- Computational Chemistry and Biology Group, CCBG, DETEMA, Facultad de Química, Universidad de la República, 11400 Montevideo, Uruguay
| | - Martina Kieninger
- Computational Chemistry and Biology Group, CCBG, DETEMA, Facultad de Química, Universidad de la República, 11400 Montevideo, Uruguay
| | - Nicola Tasinato
- SMART Lab, Scuola Normale Superiore, piazza dei Cavalieri 7, 56126 Pisa, Italy
| | - Zoi Salta
- SMART Lab, Scuola Normale Superiore, piazza dei Cavalieri 7, 56126 Pisa, Italy
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Zhu B, Jiang J, Lu B, Li X, Zeng X. Fluoromethylsulfinyl radicals: spectroscopic characterization and photoisomerization via intramolecular hydrogen shift. Phys Chem Chem Phys 2022; 24:8881-8889. [PMID: 35362501 DOI: 10.1039/d1cp05556a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Two new sulfinyl radicals, CHF2SO˙ and CH2FSO˙, have been generated in the gas phase through homolytic cleavage of the weak S-S bonds in disulfane oxides CHF2S(O)SCF3 and CH2FS(O)SCF3 by high-vacuum flash pyrolysis (HVFP) at ca. 500 °C. The IR spectroscopy characterization of the two fluoromethylsulfinyl radicals in solid N2 (10 K), Ar (10 K), and Ne (3 K) matrices reveals the presence of two conformers for CHF2SO˙ (gauche and cis) and one conformer for CH2FSO˙ (gauche). Upon 266 nm laser irradiation, these radicals undergo both isomerization and decomposition in the matrices. In addition to the dominant formation of the elusive oxathiyl radicals CHF2OS˙ (gauche and cis) and CH2FOS˙ (gauche) via 1,2-alkyl migration, two higher-energy carbon-centered radicals ˙CF2SOH and ˙CHFSOH bearing similar molecular structures to hydroperoxyalkyl radicals (˙QOOH) form via intramolecular 1,3-hydrogen shift in the two sulfinyl radicals. Additionally, the involvement of 1,3-hydrogen shift in CHF2OS˙ and CH2FOS˙ is also indicated by the observation of the fragmentation species. The identification of these radicals by matrix-isolation IR and UV-vis spectroscopy is aided by the quantum chemical calculations at the B3LYP/6-311++G(3df,3pd) level of theory. The stability of the isomers of the two sulfinyl radicals CHF2SO˙ and CH2FSO˙ has been discussed according to the experimental observations and also based on the CCSD(T)-F12a/aug-cc-pVTZ//B3LYP/6-311++G(3df,3pd) calculated energy profiles.
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Affiliation(s)
- Bifeng Zhu
- Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysts and Innovative Materials, Fudan University, Shanghai, 200433, China.
| | - Junjie Jiang
- Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysts and Innovative Materials, Fudan University, Shanghai, 200433, China.
| | - Bo Lu
- Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysts and Innovative Materials, Fudan University, Shanghai, 200433, China.
| | - Xiaolong Li
- Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysts and Innovative Materials, Fudan University, Shanghai, 200433, China.
| | - Xiaoqing Zeng
- Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysts and Innovative Materials, Fudan University, Shanghai, 200433, China.
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