S-Nitrosation of Aminothiones

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• 作者：Joyeth B. Dorado ; Bogdan Z. Dlugogorski ; Eric M. Kennedy ; John C. Mackie ; Jeff Gore ; Mohammednoor Altarawneh
• 刊名：Journal of Organic Chemistry
• 出版年：2015
• 出版时间：July 17, 2015
• 年：2015
• 卷：80
• 期：14
• 页码：6951-6958
• 全文大小：434K
• ISSN：1520-6904

文摘

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 K_eq corresponds to 559鈥?82 M^鈥? for thioacetamide (TA, 15鈥?5 掳C) and 12600鈥?590 M^鈥? for thiourea (TU, 15鈥?5 掳C), whereas the reaction enthalpies amount to 鈭?7.10 卤 0.05 kJ for TA and 鈭?9.30 卤 0.05 kJ for TU. Theoretical calculations via a thermochemical cycle agree well with reaction free energies from experiments, with errors of 鈭?鈥? kJ using solvation method SMD in conjunction with hybrid meta exchange鈥揷orrelation 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路mol^鈥? (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.