Affordable Access

Publisher Website

Mass spectrometric characterization of small oxocarboxylic acids and gas phase ion fragmentation mechanisms studied by electrospray triple quadrupole-MS/MS-TOF system and DFT theory

International Journal of Mass Spectrometry
Publication Date
DOI: 10.1016/j.ijms.2007.07.014
  • Oxocarboxylic Acid
  • Dft
  • Cid
  • Q-Tof
  • Fragmentation Mechanism


Abstract Monocarboxylic acids with acyl functional group such as 5-oxohexanoic acid and 6-oxoheptanoic acid were characterized experimentally by electrospray ionization coupled to a triple quadrupole and TOF analyzer hybrid system. Collision-induced dissociation experiments at different activation energies were done to elucidate possible fragmentation pathways. These pathways were also studied on the theoretical level using DFT B3LYP/6-311++G(3df,3pd)//B3LYP/6-31+G(d) + ZPVE calculations. While all monocarboxylic acids fragment under loss of CO 2 and H 2O starting from their parent anion [ M − H] −, an unusual fragmentation behaviour could be observed in case of 5-oxohexanoic acid. Synchronous CO 2 and CH 2CH 2 elimination in a concerted mechanism was responsible for the lack of [ M − H–CO 2] − fragment ion. New anionic gas phase cyclization processes could be discerned in case of 5-oxohexanoic acid. Mechanistic differences in the fragmentation pathways of [ M − H] − anions formed from 5-oxohexanoic acid and 6-oxoheptanoic acid after deprotonation were investigated both experimentally and through DFT calculations. Successive water, ketene CH 2 C O, and H 2 eliminations were observed in the CID spectra of 6-oxoheptanoic acid parent anion. CO 2 ejection from the parent ion of 6-oxoheptanoic acid was inhibited due to the lack of stabilization for the formed fragment ion.

There are no comments yet on this publication. Be the first to share your thoughts.


Seen <100 times