Insight into the chemistry of reactive intermediates from mass spectrometric gas-phase ion -molecule reaction studies
Abstract
Four ion-molecule reaction studies are described, that explore different aspects of the chemistry of reactive intermediates via mass spectrometric methods. In the first study, the reactivity of the dichlorocarbene radical cation is examined. This ionized carbene is found to react by both net-anion and net-radical abstraction with a wide variety of organic compounds. Both types of reactivity are found to occur via a single electrophilic addition-elimination mechanism. In the second study, the structure and reactivity of the 3,5-didehydrophenyl cation and several its most stable isomers were characterized. Ion-molecule reactions were found that differentiate the 3,5-didehydrophenyl cation from its isomers. Examination of the reactivity of various C6 H3+ ion populations generated by the electron ionization of 1,3,5-trisubstituted benzenes reveals that in all cases a mixture of isomers is produced, and that the 3,5-didehydrophenyl cation is present in only minor amounts in most cases. The third study explores charge site effects on the radical reactions of distonic ions by comparing the reactivity of the N-(3,5-didehydrophenyl)pyridinium and 3,5-didehydrobenzoate ions. These two oppositely charged distonic analogs of the phenyl radical exhibit similar qualitative reactivity. However, the relative rates of their reactions vary dramatically. The net effect of the charge site on the intrinsic radical reactivity of the phenyl radical moiety is to make the phenyl radical strongly electrophilic or nucleophilic, respectively. In the fourth and final study, distonic meta-benzyne analogs were found to react as electrophiles toward a wide variety of organic nucleophiles. In many cases, an addition-elimination reactivity occurs in which the attacking nucleophile replaces the distonic ion's charge site. The zwitterionic intermediate resulting from addition to the meta-benzyne moiety was trapped in several cases, and it's reactivity was studied. In some cases, when the charge-site substitution reactivity is unfavorable, the intermediates fragment to result in net-radical abstraction products.
Degree
Ph.D.
Advisors
Kenttamaa, Purdue University.
Subject Area
Analytical chemistry|Organic chemistry
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