62290-59-9Relevant academic research and scientific papers
Ion Cyclotron Resonance and Deuterium Kinetic Isotope Studies of the Gas-Phase Reactions of the Alkoxide Negative Ions with Anhydrides and Esters
Klass, Gunter,Underwood, Dennis J.,Bowie, John H.
, p. 507 - 517 (2007/10/02)
(i) The i.c.r. spectrum of CD3O-/acetic anhydride system shows the occurrence of the negative ion McLafferty rearrangement and the characteristic elimination shown in reaction (2) (R = COMe) CD3O- + (MeCO)2O -> (CD3O)(Me)(HO)C-O- + CH2CO (1), CD3O- + MeCO2R -> -CH2CO2CD3 + ROH (2). (ii) The i.c.r. spectra of CD3O-/alkyl ester systems show major peaks due to +>- ions, together with small peaks corresponding to ->- adducts.Carboxylate and alkoxide anions (derived from the ester) are also observed in certain spectra; peaks due to these ions increase in intensity with elaboration of alkyl substituents.Reaction (2) is characteristic of all esters studied (illustrated above for acetates) which have at least one hydrogen substituent on the carbon atom α to the carbonyl group.The reaction must occur by nucleophilic attack of the alkoxide anion at the carbonyl group of the ester.Negative ion McLafferty rearrangements do not occur in alkyl ester systems. (iii) The H transfer reactions (1) and (2) show deuterium isotope effects kH/kD of 3.0 and 1.5 respectively (when the carbon adjacent to the carbonyl group contains one deuterium substituent).Isotope effect calculations suggest that reaction (1) proceeds through a 'near symmetrical' six-membered transition state, whereas (2) goes through a 'reactant-like' but distorted four-centred transition state.
Gas-Phase Ion/Molecule Isotope-Exchange Reactions: Methodology for Counting Hydrogen Atoms in Specific Organic Structural Environments by Chemical Ionization Mass Spectrometry
Hunt, Donald F.,Sethi, Satinder K.
, p. 6953 - 6963 (2007/10/02)
Ion/molecule reactions are described which facilitate exchange of hydrogens for deuteriums in a variety of different chemical environments.Aromatic hydrogens in alkylbenzenes, oxygenated benzenes, m-toluidine, m-phenylenediamine, thiophene, and several polycyclic aromatic hydrocarbons and metallocenes are exchanged under positive ion CI conditions by using either D2O, EtOD, or ND3 as the reagent gas.Aromatic hydrogens, benzylic hydrogens, and hydrogens on carbon adjacent to carbonyl groups suffer exchange under negative ion CI conditions in ND3, D2O, and EtOD, respectively.A possible mechanism for the exchange process is discussed.
