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S-nitrosation of aminothiones

Dorado, J.B., Dlugogorski, B.Z., Kennedy, E.M., Mackie, J.C., Gore, J. and Altarawneh, M.ORCID: 0000-0002-2832-3886 (2015) S-nitrosation of aminothiones. The Journal of Organic Chemistry, 80 (14). pp. 6951-6958.

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Nitrosation reactions span a diverse range of applications, from biochemistry to industrially important processes. This study examines nitrosation of aminothiones in acidic solutions and re-evaluates currently accepted diffusion limits and the true nature of the nitrosating agent for nitrous acid initiated reactions. Experimental measurements from stopped-flow UV/vis spectrophotometry afforded derivation of equilibrium constants and reaction enthalpies. Apparent Keq corresponds to 559-382 M-2 for thioacetamide (TA, 15-25 °C) and 12600-5590 M-2 for thiourea (TU, 15-35 °C), whereas the reaction enthalpies amount to -27.10 ± 0.05 kJ for TA and -29.30 ± 0.05 kJ for TU. Theoretical calculations via a thermochemical cycle agree well with reaction free energies from experiments, with errors of -2-4 kJ using solvation method SMD in conjunction with hybrid meta exchange-correlation functional M05-2X and high-accuracy multistep method CBS-QB3 for gas-phase calculations. The kinetic rates increase with acidity at activation energies of 54.9 (TA) and 66.1 kJ·mol-1 (TU) for the same temperature range, confirming activation-controlled reactions. At pH 1 and below, the main decomposition pathway for the S-nitroso species leads to formation of nitric oxide. (Graph Presented).

Item Type: Journal Article
Murdoch Affiliation: School of Engineering and Information Technology
Publisher: ACS Publications
Copyright: © 2015 American Chemical Society
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