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Fragmentation reactions of the enolate ions of 2‐pentanone
Author(s) -
Donnelly Allen,
Chowdhury Swapan,
Harrison Alex. G.
Publication year - 1989
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.1210240206
Subject(s) - chemistry , fragmentation (computing) , elimination reaction , deuterium , ion , hydrogen , medicinal chemistry , reductive elimination , hydrogen atom abstraction , methyl group , photochemistry , group (periodic table) , organic chemistry , catalysis , physics , quantum mechanics , computer science , operating system
The reaction of [OH] − with 2‐pentanone produces two enolate ions, [CH 3 CH 2 CH 2 COCH 2 ] − and [CH 3 COCHCH 2 CH 3 ] − , by proton abstraction from C(1) and C(3), respectively. Using deuterium isotopic labelling the fragmentation reactions of each enolate have been delineated for collisional activation at both high (8 keV) and low (5–100 eV) collisional energies. The primary enolate ion fragments mainly by elimination of ethene. Two mechanisms operate: elimination of C(4) and C(5) with hydrogen migration from C(5), and elimination of C(3) and C(4) with migration of the C(5) methyl group. Minor fragmentation of the primary enolate also occurs by elimination of propane and elimination of C 2 H 5 ; the latter reaction involves specifically the terminal ethyl group. The secondary enolate ion fragments mainly by loss of H 2 and by elimination of CH 4 ; for the latter reaction four different pathways are operative. Minor elimination of ethene also is observed involving migration of a C(5) hydrogen to C(3) and elimination of C(4) and C(5) as ethene.