Premium
Intramolecular aromatic substitution reactions in substituted N , N ‐dimethylthiobenzamide ions
Author(s) -
Ramana Devalla Venkata,
Grützmacher HansFr.
Publication year - 1981
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.1210160508
Subject(s) - chemistry , substituent , ion , intramolecular force , protonation , kinetic energy , hydrogen atom , mass spectrum , atom (system on chip) , crystallography , stereochemistry , organic chemistry , group (periodic table) , physics , quantum mechanics , computer science , embedded system
The molecular ions of N , N ‐dimethylthiobenzamide and its ortho substituted derivatives (substituents CH 3 , Cl, Br, I) lose a hydrogen atom and/or the ortho substituent. The mechanism of this process has been studied by measurements of the ionization energies, appearance energies of the product ions m / z 164 and the kinetic energy release during this process. The structure of the product ions m / z 164 and relevant reference ions have been investigated by mass analysed ion kinetic energy spectra, B / E linked scan spectra and collision induced decompositions. The results show clearly the formation of two different kinds of product ions m / z 164 depending on the substituent lost. Type a ions are formed by loss of a H atom or the CH 3 substituent and correspond to protonated 3,4‐benzo‐ N ‐methylpyroline‐2‐thione. The formation of these ions occurs by a hydrogen rearrangement followed by an intramolecular substitution via a 5‐membered cyclic intermediate and is associated with a large release of kinetic energy. In contrast, the loss of the halogeno substituents to give type b ions probably occurs via a direct displacement reaction by the sulfur atom of the thioamide group giving rise to Gaussian shaped peaks mass analysed ion kinetic energy spectra.