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A mass spectral study of 1‐(aryldimethylsilyl)‐2‐propanones and their isomeric 2‐(aryldimethylsiloxy)‐1‐propenes
Author(s) -
Tsai Robert S.C.,
Larson Gerald L.,
Oliva Alfonso
Publication year - 1979
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.1210140705
Subject(s) - chemistry , fragmentation (computing) , enol , mass spectrum , silylation , electron ionization , ion , metastability , benzene , ether , medicinal chemistry , spectral line , crystallography , stereochemistry , ionization , organic chemistry , catalysis , physics , astronomy , computer science , operating system
The mass spectra of a series of β‐ketosilanes, p ‐YC 6 H 4 Me 2 SiCH 2 C(O)Me and their isomeric silyl enol ethers, p ‐YC 6 H 4 Me 2 SiOC(CH 3 )CH 2 , where Y = H, Me, MeO, Cl, F and CF 3 , have been recorded. The fragmentation patterns for the β‐ketosilanes are very similar to those of their silyl enol ether counterparts. The seven major primary fragment ions are [MMe·] + , [MC 6 H 4 Y·] + , [MMe 2 SiO] + ˙, [MC 3 H 4 ] + ˙, [MHCCCF 3 ] + ˙, [Me 2 SiOH] + ˙ and [C 3 H 6 O] + ˙ Apparently, upon electron bombardment the β‐ketosilanes must undergo rearrangement to an ion structure very similar to that of the ionized silyl enol ethers followed by unimolecular ion decompositions. Substitutions on the benzene ring show a significant effect on the formation of the ions [MMe 2 SiO] + ˙ and [Me 2 SiOH] + ˙, electron donating groups favoring the former and electron withdrawing groups favoring the latter. The mass spectral fragmentation pathways were identified by observing metastable peaks, metastable ion mass spectra and ion kinetic energy spectra.