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Substituent effect and rearrangements in the electron‐impact spectra of long chain esters of m ‐and p ‐methoxybenzoic acid
Author(s) -
Winnik Mitchell A.,
Kwong P. Y. Y.
Publication year - 1975
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.1210100504
Subject(s) - substituent , chemistry , mass spectrum , alkyl , oxygen , ion , spectral line , oxygen atom , hydrogen , electron ionization , medicinal chemistry , chain (unit) , stereochemistry , molecule , organic chemistry , physics , astronomy , ionization
The mass spectra of eighteen n‐alkyl estars of p‐methoxybenzoic acid are examined. Few differences exist in the spectra of the corresponding para and meta isomers. We describe a new rearrangement, loss of OH from the molecular ion, whichis observed only in the para substituted isomkers. Oxygen‐18 labeling indicates that the oxygen lost in the [MOH]+ ion derives from the carbonyl. No indication is found of hydrogen abstration from the chain by the methoxy group competing withthe benzoate ester rearrangement. We find a substituent effect on that rearrangement, with electron‐donating groups decreasing the values of [ArCO 2 H 2 ] + /[ArCO 2 H] + · ion ratios. this ratio decreases as the ester chain length increases.