Ion cyclotron resonance mass spectrometry

Ion cyclotron resonance mass spectrometry (ICR-MS) Is one of the most widely used techniques for studying gas-phase ion/molecule reactions. Physical organic properties such as basicity and acidity are often measured. This technique has been applied to two studies: measuring the gas-phase acidity of the conjugate acids of some frequently used bases in organic synthesis and determining the structures of the isomeric (M-H) anions of methyl nitrite and nitromethane. In addition a comparison is made between the different detection modes available to ICR-MS; slow passage (SP), rapid scan (RS) and Fourier transform (FT). Choice of solvent and counter ion can influence the reaction in organic synthesis. To study the intrinsic properties of compounds, measurements are made in the gas-phase in the absence of these effects. The gas-phase acidities of hexamethyldisilizane, trimethylsilanol, triethylsilanol, diisopropylamine and 2,2,6,6-tetramethylpiperidine are reported here. The gas-phase reactivity of all the anions except hexamethyldisilazide parallel their reactivity in the solution phase. Hexamethyldisilizane is a much stronger acid than anticipated and semi-empirical and ab initio calculations suggest some possible rehybridization which may be controlled by the counter ion. Further work is being pursued in this area. The isomeric (M-H) anions of methyl nitrite, nitromethane and formyl hydroxamate are studied here by means of MS/MS experiments.