title: S-Nitrosation of Aminothiones.
abstract: 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.
authors.affiliation: †Process Safety and Environment Protection Research Group, School of Engineering, The University of Newcastle, Callaghan, NSW 2308, Australia.
authors.forename: Joyeth B
authors.initials: JB
authors.lastname: Dorado
authors.affiliation: ‡School of Engineering and Information Technology, Murdoch University, 90 South Street, Murdoch 6150, WA, Australia.
authors.forename: Bogdan Z
authors.initials: BZ
authors.lastname: Dlugogorski
authors.affiliation: †Process Safety and Environment Protection Research Group, School of Engineering, The University of Newcastle, Callaghan, NSW 2308, Australia.
authors.forename: Eric M
authors.initials: EM
authors.lastname: Kennedy
authors.affiliation: †Process Safety and Environment Protection Research Group, School of Engineering, The University of Newcastle, Callaghan, NSW 2308, Australia.
authors.forename: John C
authors.initials: JC
authors.lastname: Mackie
authors.affiliation: §Dyno Nobel Asia Pacific Pty Ltd., Mt Thorley Technical Centre 5, Woodlands Road, Mt. Thorley 2330, NSW, Australia.
authors.forename: Jeff
authors.initials: J
authors.lastname: Gore
authors.affiliation: ‡School of Engineering and Information Technology, Murdoch University, 90 South Street, Murdoch 6150, WA, Australia.
authors.forename: Mohammednoor
authors.initials: M
authors.lastname: Altarawneh
mesh_terms: D000143:Acids / Q000737:chemistry; D007700:Kinetics; D009569:Nitric Oxide / Q000737:chemistry*; D015538:Nitrosation; D011789:Quantum Theory; D012996:Solutions / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics; D013871:Thiones / Q000737:chemistry*
chemical_list: D000143:Acids; D012996:Solutions; D013871:Thiones; D009569:Nitric Oxide