Neutral Products from Ionic Reactions in the Gas Phase

University Of California-Riverside, Riverside CA

Investigators

Abstract

With the support of the Organic Dynamics Program in the Chemistry Division, Professors Thomas H. Morton at University of California- Riverside explores the neutral products formed by reactions of positive ions with neutral molecules in the vapor phase. Gas phase ion chemistry has been extensively explored by many research groups using mass spectrometric techniques, but a number of crucial questions about the structures and reactivities of positive ions can be addressed only by looking at the electrically uncharged products of their reactions with nucleophiles or Bronsted bases. Three techniques are described for producing isolable yields of neutral products from gaseous cationic reactions: (1) Nuclear decay of organic molecules containing 2 tritium atoms. b-Particle ejection from one of those nuclei yields an ion that still retains a single tritium; hence, neutral products of its ion-molecule reactions can be detected by virtue of their remaining radioactivity, (2) Electron impact on C1 and C2 halocarbons as targets in an Electron Bombardment Flow (EBFlow) reactor. Apart from the potential environmental relevance of the products of their ionization, the even-electron ions resulting from loss of a halogen atom can react with a variety molecules to give neutrals, whose isomeric distributions will answer questions regarding the factors that underlie kinetic control of stereochemistry in the absence of solvent, and (3) Injection of monatomic and diatomic ions into reactive gases. High intensity ion sources are extensively used by physicists in accelerators that first produce negative ions and then strip electrons from them to make positive ions. Adaptation of such a source to chemical experiments increases the scope of bimolecular reactions that can be studied by organic chemists. The Organic and Macromolecular Chemistry Program in the Chemistry Division supports Professor Thomas H. Morton at University of California- Riverside who proposes several hypotheses regarding organic reactivity that can be tested by looking at neutral products from ionic reactions in the gas phase. These include a variety of fundamental questions about Lewis acid-base chemistry. Understanding the origin of stereoselectivity and increasing the yield of chemical reactions represent two major aspects of organic chemical research. Professor Morton's work will describe ways in which ion-molecule reactions might be harnessed to provide useful quantities of molecules that have not been previously prepared or give products that can be more efficiently formed and recovered from gaseous reaction mixtures. Examples include radio labelled compounds used for nuclear medicine and fluorine-containing molecules that have not been synthesized in any other way. This work will provide training for graduate and undergraduate students in several important areas of chemistry: organic reactions mechanisms, experimental physical chemistry, computations, and mass spectrometry.