The mass spectra of Schiff bases. I. Simple fissions and rearrangements

Abstract

Under electron impact, Schiff bases give a stable molecular ion which undergoes simple fission at the ring-nitrogen and ring-carbon bonds. Ortho substitution leads to ions derived from five-membered heterocycles. Derivatives of o-methoxy-benzaldehyde exhibit a two-hydrogen transfer with fission of the azomethine double bond to give the amine radical-ion.

Synthesis and Characterization of Some Dibasic Tridentate Schiff Base Ligands

“…The formation of such stable heterocyclic species is characteristic of the mass spectra of orthosubstituted aromatic Schiff bases (12).…”

Ortho effects in organic molecules on electron impact: 18—Novel hydrogen transfer from the methoxy group to acetylenic carbon in 2‐methoxyphenylacetylene and 2‐methoxydiphenylacetylenes

“…l(a), (b) and (d) that the mass spectrum of 2-methoxyphenylacetylene does contain peaks corresponding to both the ortho interaction of the methoxy group and those due to the characteristic decomposition of the aromatic methoxy group. Similar ortho interaction of the methoxy group is also noticed in 2-methoxydiphenylacetylene (6). Drawing an analogy from compound 1, a 3-phenyl-2H-1-benzopyran structure c is assigned to the rearranged molecular ion which undergoes a variety of fragmentation processes as shown in Schemes 2 and 3.…”

An electron impact study of the two isomeric tricarbonylchromium complexes of N-benzylideneaniline

“…SAlthough the m* associated with mle 233 -t mle 78 also holds for mle 317 + mle 91 (C=N fission), we neglect this latter transition on energetic grounds; indeed, we were unable to detect metastable peaks for the corresponding C=N fission steps in m/e 289,261, or 233, all of which should be energetically more amenable to such fission than the parent ion, and even in the uncomplexed benzylideneaniline the incidence of azomethine double bond fission is remarkably low (22).…”

“…In addition to the fragment ion peaks discussed in the foregoing, which are derived from chromium-containing species, the spectrum in the lower mass-number range extending up to mle 181 shows the typical fragmentation pattern of benzylideneaniline (22,25) as verified by comparison with the mass spectrum of this compound recorded separately under identical conditions. Additionally, the characteristic [C,H,lf peak at mle 51 (through expulsion of acetylene from phenyl cation) should be mentioned, as should the low-intensity peaks at mle 63, 64, 78, and 89.…”

“…In the previous papers (22,25) the generation of mle 77 in the fragmentation of benzylideneaniline was accounted for in terms of loss of C,H6N' from mle 181 (m* reported at mle 32.8). However, we find the metastable peak more accurately at mle 32.9, reflecting the transition mle 180 + mle 77, and this step in fact appears more plausible than mle 181 -t mle 77 on energetic grounds.…”