Intramolecular hydrogen transfer as the key step in the dissociation of hydroxyl radical adducts of (alkylthio)ethanol derivatives
作者:Christian Schoneich、Krzysztof Bobrowski
DOI:10.1021/ja00068a010
日期:1993.7
hydroxyl radical adduct of DMS dissociates into a sulfur radical cation and HO[minus] in the thioether concentration-independent pathway (k[sub H]/k[sub D] = 2.09), whereas a rate-limiting proton transfer from water operates in the thioether concentration-dependent mechanism (k[sub H]/k[sub D] = 5.40), as deduced from the measured solvent kinetic isotope effects. In contrast the hydroxyl radical adducts
羟基自由基与二甲硫醚 (DMS)、2-(甲硫基)乙醇 (2-MTE)、2,2'-二羟基二乙基硫醚 (2,2'-DHE) 和 3,3'-二羟基二丙基硫醚的反应 ( 3,3'-DHP) 已在 H [sub 2] O 和 D [sub 2] O 中进行了研究。作为第一步,羟基自由基添加到硫部分。这些羟基自由基加合物随后通过硫醚浓度依赖性和硫醚浓度非依赖性途径衰变。DMS 的羟基自由基加合物在与硫醚浓度无关的途径中解离为硫自由基阳离子和 H2O[minus](k[sub H]/k[sub D] = 2.09),而来自水的限速质子转移起作用在硫醚浓度依赖机制中 (k[sub H]/k[sub D] = 5.40),从测得的溶剂动力学同位素效应推导出来。相比之下,2-MTE 和 2,2'-DHE 的羟基自由基加合物通过消除水分解,通过相邻羟基的快速分子内氢转移形成。这种机制导致(烷硫基)乙氧基的形成。
Rate coefficients for the gas-phase reaction of OH radicals with dimethyl sulfide: temperature and O<sub>2</sub>partial pressure dependence
作者:Mihaela Albu、Ian Barnes、Karl H. Becker、Iulia Patroescu-Klotz、Raluca Mocanu、Thorsten Benter
DOI:10.1039/b512536g
日期:——
coefficients for the gas-phase reaction of hydroxyl (OH) radicals with dimethyl sulfide (CH(3)SCH(3), DMS) have been determined using a relative rate technique. The experiments were performed under different conditions of temperature (250-299 K) and O(2) partial pressure (approximately 0 Torr O(2)-380 Torr O(2)), at a total pressure of 760 Torr bath gas (N(2) + O(2)), in a 336 l reaction chamber, using long path
Hydroxyl radical adduct at sulfur in substituted organic sulfides stabilized by internal hydrogen bond
作者:Krzysztof Bobrowski、Christian Schdneich
DOI:10.1039/c39930000795
日期:——
The stability of an OH radical adduct at sulfur atoms in substituted organic sulfides is greatly enhanced by the formation of an internal hydrogen bond between the hydroxyl hydrogen and an oxygen located either in an adjacent carbonyl or methoxy group; the first absoluterate constants of the reactions of such adducts with molecular oxygen are reported.
By use of pulse radiolysis the one-electron reduction potentials, E0(DMS•+/DMS) and E0((DMS)2•+/2DMS) (dimethyl sulfide, DMS) were determined to be 1.66 ± 0.03 and 1.40 ± 0.02 V vs NHE, respectively. DMS•+ was found to be in equilibrium with DMSOH• with a pKa = 10.2. The conditional equilibrium constant for the reaction DMSOH• + DMS ⇌ (DMS)2•+ + OH- was found strongly dependent on both ionic strength
通过脉冲辐解,单电子还原电位E 0(DMS •+ / DMS)和E 0((DMS)2 •+ / 2DMS)(二甲基硫醚,DMS)被确定为1.66±0.03和1.40±相对于NHE分别为0.02V。发现DMS •+与DMSOH •处于平衡状态,ap K a = 10.2。条件平衡常数反应DMSOH • + DMS⇌(DMS)2 •+ + OH -被发现强烈地依赖于两者的离子强度和DMS的浓度。在热力学极限下,该平衡常数约为1.3。二聚反应DMS•+ + DMS⇌(DMS)2 •+具有平衡常数在10 4和5×10 4 M -1之间。DMSOH •与O 2的反应速率常数为2×10 8 M -1 s -1,与pH值(11-14)无关。根据此观察结果和其他观察结果,我们估计DMSOH •的去质子化的p K a超过17。根据光谱和动力学数据,自由基(DMS)2 OH •的最大寿命预计为10 ns。DMS-X的稳定性•水溶液中的(X