Thoen K K, Pérez J, Ferra J J, Kenttämaa H I
Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-1393, USA.
J Am Soc Mass Spectrom. 1998 Nov;9(11):1135-40. doi: 10.1016/S1044-0305(98)00097-X.
The feasibility of generating substituted phenyl radicals and biradicals (with a charged substituent) in the gas phase by laser photolysis was examined by using a Fourier-transform ion cyclotron resonance mass spectrometer. The precursors were generated by ipso-substitution of a halogen atom in the radical cation of a di- or trihalobenzene by various nucleophiles. Photolytic cleavage of the remaining carbon-halogen bond(s) with 266-nm radiation was found to produce many substituted phenyl radicals in greater yields than the earlier employed method, sustained off-resonance irradiated collision-activated dissociation (SORI-CAD). Furthermore, ion generation by photolysis leads to isomerization less often than collisional activation. Finally, not only phenyl-bromine and phenyl-iodine but also certain phenyl-chlorine bonds can be cleaved by photolysis, whereas the synthetic utility of SORI-CAD appears to be largely limited to the cleavage of phenyl-iodine bonds. Hence, laser photolysis greatly expands the variety of substituted phenyl radicals and biradicals that can be synthesized inside a mass spectrometer.
利用傅里叶变换离子回旋共振质谱仪，研究了通过激光光解在气相中生成取代苯基自由基和双自由基（带有一个带电取代基）的可行性。前体是通过各种亲核试剂对二卤代苯或三卤代苯的自由基阳离子中的卤原子进行本位取代而生成的。发现用266纳米辐射光解剩余的碳 - 卤键，与早期使用的持续非共振辐照碰撞活化解离（SORI - CAD）方法相比，能以更高的产率生成许多取代苯基自由基。此外，光解产生离子的异构化频率比碰撞活化更低。最后，不仅苯基 - 溴键和苯基 - 碘键，某些苯基 - 氯键也能通过光解断裂，而SORI - CAD的合成效用似乎在很大程度上限于苯基 - 碘键的断裂。因此，激光光解极大地扩展了可在质谱仪内合成的取代苯基自由基和双自由基的种类。
