Identification and reactivity of distonic radical cations

Krista Marie Stirk, Purdue University

Abstract

The study of distonic radical cations, ions with spatially separated charge and radical sites, is a relatively new field in organic mass spectrometry. Initial interest in these ions stemmed from the fact that distonic ions are often more stable than other isomeric structures. Now it is known that distonic ions are both stable and common gas phase species and that the study of these ions will lead to a deeper understanding of many organic reactions. The identification and reactivity of distonic ions were investigated using a Fourier transform ion cyclotron resonance mass spectrometer. The identification of distonic ions was carried out primarily by ion-molecule reactions, although low-energy collision-activated dissociation also proved to be useful in several instances. Ion-molecule reactions useful in the structural characterization of distonic ions include the transfer of a radical cation from a distonic ion to a nucleophile and the abstraction of an atom or group by the ion. The reactivity of distonic ions is, however, difficult to generalize. In this thesis, three types of reactions of distonic ions are recognized. Some ion-molecule reactions of distonic ions seem to involve only the charged site of the ion. In these cases, similar reactions are observed for distonic ions and their even-electron counterparts. Reactions involving predominantly the radical site have also been observed: in particular, distonic ions with coordinatively saturated charged sites react at the radical site. Other ion-molecule reactions are proposed to involve the cooperation of both reactive sites. Some distonic ions are primarily unreactive, and these ions are discussed separately. A third consideration in the study of distonic ions is the formation of these ions. In this thesis, both unimolecular and bimolecular reactions have been used to effectively generate $\alpha$-, $\beta$-, and $\gamma$-distonic ions of diverse structures. This work provides a basis for various further studies on distonic ions, some of which are outlined.

Degree

Ph.D.

Advisors

Kenttamaaa, Purdue University.

Subject Area

Analytical chemistry|Organic chemistry

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