Determination of double bonds in alkenes by field ionization mass spectrometry

Abstract

Electron impact (El), metastable ion (MI), and field ionization mass spectra of isomeric linear alkenes (C4-C8) are reported. In contrast to the identical MI and similar El spectra of these compounds, the FI spectra show pronounced differences in the fragmentation pattern. They are dominated by fragments due to allylic cleavage which allows an unequivocal location of the double bond. In general, allylic cleavage leads also to the most abundant fragment in branched double bond isomers although a few exceptions are observed with these compounds.

Location of conjugated diene position in an aliphatic chain by mass spectrometry of the 4-phenyl-1,2,4-triazoline-3,5-dione adduct

“…1986,13,395. (10) Cotter, R. J.; Larsen, B. S.; Heller, D. N.; Campana, J. E.; Fenselau, C, Anal. Chem.…”

“…Isobutane Cl mass spectrometry of conjugated dienes yields abundant diagnostic fragment ions (9). Field ionization conditions produce spectra in which double bond migration is not observed and in which allylic cleavages result in major ions that are indicative of the position of the double bond (10). Some of these methods, which require a relatively sophisticated instrumental approach, may not always be available to the general chemical practitioner Methods involving electron impact ionization usually require chemical modifiction of the double bond to form derivatives that direct the fragmentation around it in order to indicate its position.…”

“…Most obvious (because it has been most emphasized) is the fact that many kinds of "fields" or "driving forces" can be applied transversely across the FFF channel to induce the necessary migration of particles and macromolecules perpendicular to the channel flow axis. Included are sedimentation, electrical, thermal gradient, crossflow, and magnetic driving forces, each with different characteristics and different areas of applicability (10). Less well-known is the fact that there are many possible modes of operation, depending on the nature of the steady-state distribution formed by the transverse driving force (11).…”