Off-campus UNL users: To download campus access dissertations, please use the following link to log into our proxy server with your NU ID and password. When you are done browsing please remember to return to this page and log out.
Non-UNL users: Please talk to your librarian about requesting this dissertation through interlibrary loan.
Part I: Investigation of ion-molecule reactions between the benzene radical cation and weak nucleophiles. Part II: The formation and properties of gas phase arenium ions
Abstract
The reactions of the benzene radical cation with neutral hydrocarbons are the subject of the first portion of this thesis. The collisionally activated dissociation (CAD) spectrum of the ion-molecule adduct produced in the reaction of the benzene radical cation and neutral 1,3-butadiene changes dramatically as a function of the degree of collisional stabilization. This observation is interpreted in terms of two distinct structures for the adduct. The species that is stabilized has a CAD spectrum similar to the 2-phenyl-2-butene radical cation. The unstabilized structure has a CAD similar to that of 1-methylindan. The results are interpreted in terms of a two-step cycloaddition mechanism. The reaction of the benzene radical cation with neutral cyclopropane yields a mixture of both the n-propylbenzene and 8,9-dihydroindan radical cation. The initially formed adduct is a covalent distonic species which then undergoes free radical based isomerization to the aforementioned radical cation species. The benzene radical cation formed at threshold is unreactive with neutral ethylene. However, when formed with sufficient energy, the benzene radical cation forms a C$\sb8$H$\sb{10}\sp+$ adduct ion. The benzene/ethylene adduct ion possesses properties that differ from those of any of the seven reference C$\sb8$H$\sb{10}\sp+$ species investigated. The general properties and means for producing gas-phase arenium ions are the focus of the second portion of this thesis. Evidence is presented for the coexistence of $\sigma$- and $\pi$-complexes in the protonation of arenium ions in the gas phase. It was established that identical ions are produced by protonation as are by alkylation (i.e., EAS). The existence of the $\pi$-complex is consistent with the observation that the alkyl moieties of secondary butyl and pentyl benzenium ions isomerize prior to decomposition. The collision complex formed in the ion-molecule reaction of the benzene radical cation and neutral alkyl iodides were shown to be nonisomerizing iodonium radical cation adducts that dissociate to gas-phase arenium ions. The benzene radical cation also forms collision complexes with bromoalkanes, although these adducts do not form arenium ions.
Subject Area
Organic chemistry|Analytical chemistry
Recommended Citation
Holman, Robert William, "Part I: Investigation of ion-molecule reactions between the benzene radical cation and weak nucleophiles. Part II: The formation and properties of gas phase arenium ions" (1988). ETD collection for University of Nebraska-Lincoln. AAI8824932.
https://digitalcommons.unl.edu/dissertations/AAI8824932