Fast-atom-bombardment-induced reduction of aromatic oximes

Abstract

Aromatic oximes and /?-hydroxyoxlmes are reduced to their corresponding Imines by Interaction of their solutions In glycerol solvent with a 7-keV argon atom beam. Evidence that the reduction occurs for the protonated oximes comes from fast atom bombardment (FAB) mass spectrometry, tandem mass spectrometry, and time-resolved FAB studies. The requirement that the oxime be In solution was established by comparing the FAB results with those obtained by electron Ionization, chemical Ionization, and laser desorption. The time-dependent studies of the concentration of the protonated oxime and the reduced product, a protonated Imlne, were made with and without added anionic surfactant. The abundance of the reduced species depends on the concentration of the protonated oxime at the matrix surface, thus showing that the first step of the reduction mechanism Is the protonation of the analyte, followed by reduction and eventual desorption of the reduced species. Surface reduction occurs for all the compounds containing an oxime group that were studied and Is a useful characteristic for Identifying oximes by fast atom bombardment mass spectrometry.

Beam‐induced dehalogenation in LSIMS: Effect of halogen type and matrix chemistry

“…These dyes are the most extensively studied system^.^-'^ In certain instances, a specific functional group of the analyte is known to be involved in the reductive process. Examt Author to whom correspondence should be addressed ples include the reduction of nitroI4 and azideI5 groups to the amine, reduction of aromatic oximes to imines, 16 dehydroxylation' (substitution of a hydroxy function by a hydrogen), deamination" (substitution of a primary amine by a hydrogen), reduction cf disulfides to thiols" and dehalogenation' 5 * 2 0 -2 5 (substitution of a halogen by a hydrogen).…”

Beam-induced reaction between meta-nitrobenzyl alcohol and dipyridocyanine dyes in liquid-secondary-ion mass spectrometry

“…The adduct ions observed in the LSIMSmass spectra of these dipyridocyanine dyes are formed in an addition reaction that formally corresponds to deoxygenation of the solvent matrix molecule. As such, the reaction represents a type of reduction reaction initiated by the primary ion beam reported in only a few other instances [15][16][17]. A significant difference here is that the deoxygenation involves the matrix rather than the sample molecule.…”

Improving fast atom bombardment mass spectra: The influence of some controllable parameters on spectral quality

“…Optimally, the desorption ionization process generates molecular or quasimolecular ions as well as structurally significant fragments; however, many beam-induced reactions can occur that alter the structure of the analyte molecule. In addition to unimolecular fragmentation (a manifestation of beam-induced thermal "damage"), these reactions include adduct formation between the matrix and analyte [3], halogen replacement [4], reduction involving electrons [5,6] and/or hydrogen atom(s) [5,7], and metal exchange involving organometallics and the metallic FAB probe tip [8]. These latter reactions are all examples of beam-induced chemical damage, that is, damage resulting from intermolecular interactions with the products of thermal damage (fragments or electrons).…”