Electron‐impact studies—LI: Hydrogen randomization in the stilbene molecular ion

Abstract

Hydrogen randomization precedes the formation of M+--H. and M+. -CH; species from the stilbene molecular ion at 15 eV. The carbon atom involved in the M+. -CH; elimination originates randomly from the whole molecule. The [M -151 ion (m/e 165) in the spectra of stilbene and 9,lO-dihydrophenanthrene is produced from a common ion.

Mass spectrometry of N‐substituted amino acids and their derivatives: Correlation of the abundances of the M+. and selected fragment ions of metamers

“…It should be pointed out that 9,lO-dihydrophenantrene-type structures of the molecule ions a of 1-16 shown in Schemes 1-3 are conjectural, but consistent with previously published literature data.l6sI7 The principal mass fragmentation pathways of N-substituted amino acids (3,6,9,12,15,17,19) are similar to those of their metameric methyl esters (1, 4, 7, 10, 13, 16, 18) and hydrazides (2, 5, 8,11,14) but show differences in the abundances of the important ions.…”

“…The N-substituted 8-phenyl-8-alanines (17,19) may be distinguished from their metameric methyl esters of N-phenylglycines (16,18) on the basis of the highest values of pl and pz .…”

“…the ratio of intensity of the selected fragment ions peaks to that of the parent ion peak. This paper deals with the elucidation of the mass fragmentation of the N-(E)-stilbenyloxyalkylcarbonyl-(or 4'-chlorostilbenyloxyalkylcarbonyl)-substituted derivatives of a-alanine, /?-phenyl-/?-alanine, N-phenylglycine and tryptophan (3,6,9,12,15,17,19) and their metameric methyl esters (1, 4, 7, 10, 13, 16, 18) and hydrazides (2,5,8, 11, 14) (Fig. 1).…”

“…The values of p,-pr calculated from the EI mass spectra recorded at 75 eV (15 eV)P of N-(E)stilbenyloxyalkylcarbonyl-substituted a-alanine (3) and fbphenyl-Palanines (6, 9) and their metameric methyl esters (1, 4, 7) and hydrazides (2, 5, 8) and of N-(E)-stilbenyloxyalkylcarbonylsubstituted tryptophan (12, 15) and their metameric methyl esters (10, 13) and hydrazides(11,14) and of N-(E)-stilbenyloxyalkylcarbonyl-substituted /I-phenyl-/I-alanines(17,19) and their metameric methyl esters(16,18) …”

Electron ionization mass spectrometric study of N‐substituted hydrazones of isomeric hydroxybenzaldehydes and isomeric pyridinecarboxaldehydes bearing an N‐(E)‐stilbenyloxyalkylcarbonyltryptophyl substituent

“…It should be pointed out that the 9,10-dihydrophenanthrene-based structures of this ion and of other stilbenes containing the structures given in Schemes 1 and 2 are conjectural but consistent with pre-viously published data. [17][18][19] Further decomposition of these ions has been widely reported. 20 In the second step of fragmentation, ion c eliminates a radical by simple a cleavage to yield odd-electron ion i.…”