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Mass spectometry in structural and stereochemical problems—CLXVIII. Effect of fluorine substitution on the McLafferty rearrangement of aliphatic ketones.
Author(s) -
Carpenter Wayne,
Duffield A. M.,
Djerassi Carl
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.1210020310
Subject(s) - chemistry , trifluoromethyl , mass spectrum , hydrogen atom , fluorine , carbon atom , methyl group , stereochemistry , alkyl , medicinal chemistry , walden inversion , photochemistry , computational chemistry , organic chemistry , ion
The mass spectra of allphatic ketones are drastically altered following substitution of a trifluoromethyl entity adjacent to the carbonyl group (II and III) or attachment to the γ‐carbon atom (V). Loss of the trifluoromethyl group by α‐cleavage far exceeds the alternative elimination of an alkyl radical. Virtually complete repression of the McLafferty rearrangement process (I → a) occurs when a CF 3 group is attached to the γ‐carbon atom. A fluorine atom is not transferred in lieu of hydrogen in the McLafferty rearrangement as demonstrated by the mass spectrum of 1,1,1,7,7,7‐hexafluoroheptan‐4‐one (IV). Rationalization for these results are presented as is a description of the syntheses of several hitherto unknown fluorinated ketones.