Electron-induced dissociation of doubly protonated betaine clusters: controlling fragmentation chemistry through electron energy.
The [M21+2H]2+ cluster of the zwitterion betaine, M = (CH3)3NCH2CO2, formed via electrospray ionisation (ESI), has been allowed to interact with electrons with energies ranging from >0 to 50 eV in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. The types of gas-phase electron-induced dissociation (EID) reactions observed are dependent on the energy of the electrons. In the low-energy region up to 10 eV, electrons are mainly captured, forming the charge-reduced species, {[M21+2H]+*}*, in an excited state, which stabilises via the ejection of an H atom and one or more neutral betaines. In the higher energy region, above 12 eV, a Coulomb explosion of the multiply charged clusters is observed in highly asymmetric fission with singly charged fragments carrying away more than 70% of the parent mass. Neutral betaine evaporation is also observed in this energy region. In addition, a series of singly charged fragments appears which arise from C-X bond cleavage reactions, including decarboxylation and CH3 group transfer. These latter reactions may arise from access of electronic excited states of the precursor ions.
Feketeová
Linda
L
School of Chemistry, University of Melbourne, Victoria 3010, Australia. lfe@unimelb.edu.au
O'Hair
Richard A J
RA
D001622:Betaine / Q000737:chemistry*; D004583:Electrons; D007477:Ions / Q000737:chemistry; D007700:Kinetics; D013058:Mass Spectrometry; D011522:Protons; D013816:Thermodynamics
D007477:Ions; D011522:Protons; D001622:Betaine