Department of Chemistry, Purdue University, West Lafayette, Indiana, USA.
J Am Soc Mass Spectrom. 1996 Dec;7(12):1245-50. doi: 10.1016/S1044-0305(96)00107-9.
Dimethyl diselenide is demonstrated to be among the most powerful reagents used to identify distonic radical cations. Most such ions readily abstract CH3Se from dimethyl diselenide. The reaction is faster and more exclusive than CH3S(·) abstraction from dimethyl disulfide, a reaction used successfully in the past to identify numerous distonic ions. Very acidic distonic ions, such as HC(+)(OH)OCH 2 (·) , do not undergo CH3Se(·) abstraction, but instead protonate dimethyl diselenide. In sharp contrast to the reactivity of distonic ions, most conventional radical cations were found either to react by exclusive electron transfer or to be unreactive toward dimethyl diselenide. Hence, this reagent allows distinction of distonic and conventional isomers, which was demonstrated directly by examining two such isomer pairs. To be able to predict whether electron transfer is exothermic (and hence likely to occur), the ionization energy of dimethyl diselenide was determined by bracketing experiments. The low value obtained (7.9±0.1 eV) indicates that dimethyl diselenide will react with many conventional carbon-, sulfur-, and oxygen-containing radical cations by electron transfer. Nitrogen-containing conventional radical cations were found either to react with dimethyl diselenide by electron transfer or to be unreactive.
二甲基二硒醚被证明是用于鉴定离域正碳离子最有效的试剂之一。大多数这样的离子很容易从二甲基二硒醚中提取 CH3Se。该反应比过去成功用于鉴定众多离域离子的从二甲基二硫醚中提取 CH3S(·)的反应更快、更具排他性。非常酸性的离域正碳离子，如 HC(+)(OH)OCH2(·)，不会发生 CH3Se(·)提取，而是质子化二甲基二硒醚。与离域离子的反应性形成鲜明对比的是，大多数常规自由基阳离子要么通过排他性的电子转移反应，要么对二甲基二硒醚不反应。因此，这种试剂允许区分离域和常规异构体，这直接通过检查两个这样的异构体对来证明。为了能够预测电子转移是否是放热的（因此很可能发生），通过内标实验确定了二甲基二硒醚的电离能。获得的低值（7.9±0.1 eV）表明，二甲基二硒醚将通过电子转移与许多常规的含碳、硫和氧的自由基阳离子反应。含氮的常规自由基阳离子要么通过电子转移与二甲基二硒醚反应，要么不反应。
