REACTIVE SPECIES BY FTMS: FREE RADICALS AND ELECTRON-DEFICIENT MAIN GROUP ATOMS

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。我们正在研究将合适的前体种子放入超音速光束中，作为跟踪离子与自由基和其他活性物质反应的手段。我们的测试反应是储存在FTMS细胞中的苯自由基阳离子与1,5-己二烯热解产生的烯丙基自由基的反应。所有的反应都在一个专门设计的FT质谱仪中进行，然后在喷嘴中以T = 1273 K在线热解1,5-己二烯。使用氘化苯和PM3水平的半经验MO计算的研究为机理提供了见解。当热解不完全时，可以观察到起始的1,5-己二烯和产物烯丙基自由基。加合物离子的产生表明烯丙基自由基的存在。用电子束电离反应束的研究表明，在种子自由基束进入FT-ICR细胞时，发生了电荷交换和m/ z91离子的形成。然而，[加合物- H]不跟踪自由基束的起始；相反，它被延迟了3毫秒。反应物质在反应前必须比从喷嘴到细胞的距离要长得多。现在仪器已经建成，系统工作，我们打算更好地表征实验系统，并扩展到缺乏电子的含硅系统和生物系统的反应，自由基损伤会导致生物功能的严重改变。我们还使用离子阱技术直接跟踪其他活性物质（例如，CBr+, SiH+, PBr+）与小有机分子的反应。此外，我们正在使用密度泛函理论来增强这些实验研究，该理论是通过运行在小型戴尔集群上的高斯98套件实现的。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We are investigating pyrolysis of suitable precursors seeded into a supersonic beam as a means to follow reactions of ions with radicals and other reactive species. Our test reaction is that of the benzene radical cation, stored in an FTMS cell, and the allyl radical generated by pyrolysis of 1,5-hexadiene. All reactions were performed in a specially designed FT mass spectrometer, following on-line pyrolysis of 1,5-hexadiene at T = 1273 K in the nozzle. Studies using deuterated benzene and semiempirical MO calculations at the PM3 level give insight to mechanism. When the pyrolysis is incomplete, both the starting 1,5-hexadiene and the product allyl radical are observed. The production of adduct ions indicate the presence of allyl radical. Studies in which an electron beam is used for ionization of the reactive beam showed that both charge exchange and formation of ions of m/z 91 occur at the time the seeded radical beam enters the FT-ICR cell. The [adduct - H], however, does not track the onset of the radical beam; instead, it is delayed by 3 ms. The reactive species must travel a considerably longer distance than that from the nozzle to the cell before reacting. Now that the instrumentation is built and the system working, we intend to characterize better the experimental system and expand to reactions of electron-deficient silicon-containing systems and to biological systems where free radical damage can cause serious modification in biological function. We are also using ion trap technology to follow directly the reactions of other reactive species (e.g., CBr+, SiH+, PBr+) with small organic molecules. In addition, we are augmenting these experimental studies with theoretical calculations by using density functional theory which is implemented through the Gaussian 98 suite running on a small Dell cluster.