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Substituent effects in the fragmentation reactions of acetanilides and phenyl acetates
Author(s) -
Shapiro Robert H.,
Tomer Kenneth B.
Publication year - 1969
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210020604
Subject(s) - substituent , acetanilide , chemistry , fragmentation (computing) , mass spectrum , ion , cleavage (geology) , medicinal chemistry , ionization , stereochemistry , computational chemistry , organic chemistry , geotechnical engineering , fracture (geology) , computer science , engineering , operating system
The mass spectra of a group of m ‐ and p ‐substituted acetanilides were measured to determine the effect of the substituents, if any, on the rate of C 2 H 2 O expulsion (rearrangement) vs. the rate of [CH 3 CO] + formation (simple cleavage). Our results agree with observations of others in that substituents which raise the ionization potential of the aromatic ring appear to localize, on the average, less charge density on this locus, and conversely. The atomic composition of the substituent, however, irrespective of its position, seems to determine the relative rates of the competing reaction. Although in several cases Z m / Z p values were close to unity, rearrangement of isomeric molecular ions to a common species is shown not to occur.