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I. Gas-phase reactions of transition metal cations with organic molecules. II. Interactions of protons and alkali metal ions with gas-phase macrolide antibiotics
Abstract
This thesis combines two topics of gas-phase ion-molecule chemistry: the reactions of transition metal cations with simple organic molecules and the interactions of protons and alkali metal ions with large, multi-functional biomolecules. The major foci of this work are the interactions of Cu(I) and Fe(I) with bicyclic compounds and of Cu(I) with alkynes. These chapters are preceded by an overview of gas-phase transition metal ion-molecule chemistry as studied by tandem mass spectrometry and high energy collisional activation. Finally, the reactivity of protonated and alkali metal-cationized macrolide antibiotics is presented. Valence isomerization and cycloreversion are observed for reactions of Cu(I) and Fe(I) with bicyclic compounds. Upon complexation with either Cu(I) or Fe(I), quadricyclane undergoes valence isomerization to norbornadiene. Both metal ions are sufficiently reactive to cause the norbornadiene ligand to rearrange by cycloreversion to a cyclopentadiene-acetylene complex. The Cu(I) complexes remain fixed as (C$\sb5$H$\sb6$)Cu$\sp+$(C$\sb2$H$\sb2$) but the Fe(I) complexes undergo an additional reaction through a hydrido-cyclopentadienyl intermediate to generate (C$\sb5$H$\sb6$)Fe$\sp+$(C$\sb2$H$\sb2$) and (C$\sb5$H$\sb5$)Fe$\sp+$(C$\sb2$H$\sb3$). Hydride abstraction and activation of both propargylic C-C bonds and remote C-H bonds are observed for reactions of Cu(I) and alkynes. Oxidative addition of Cu(I) into propargylic C-C bonds forms an (alkyne)Cu$\sp+$(alkene) complex that generally eliminates the alkene. Activation of remote C-H bonds of alkynes by Cu(I) occurs to eliminate hydrogen and small alkenes. Loss of CuH from Cu(I) complexes is consistent with abstraction of hydrides in close proximity to the site of metal complexation. The pathway occurs to little or no extent from adducts of octynes with other transition metals. Alkali metal cations and protons are observed to interact with different sites on macrolide antibiotics. The chemistry exhibited by protonated macrolides is consistent with the likely site of protonation being the dimethylamino entity of the pendant amino sugar. For cationized macrolides, however, the charge site is most likely to be on the highly oxygenated aglycone.
Subject Area
Analytical chemistry
Recommended Citation
MacMillan, Denise K, "I. Gas-phase reactions of transition metal cations with organic molecules. II. Interactions of protons and alkali metal ions with gas-phase macrolide antibiotics" (1991). ETD collection for University of Nebraska-Lincoln. AAI9219379.
https://digitalcommons.unl.edu/dissertations/AAI9219379