44870-01-1Relevant articles and documents
ROH Molecule Assisted Elimination of F- from (CF3)2CH- and (CF3)2CD- in Gas-Phase Elcb-Type Reactions
McDonald, Richard N.,McGhee, William D.,Chowdhury, A. Kasem
, p. 7334 - 7340 (1987)
The gas-phase reactions of the carbanion (CF3)2CH- with the following series of ROH molecules, (CF3)2CHOH, CF3CH2OH, (CH3)3COH, CH3OH, and H2O, are described.In each case, formation of ROH assisted Elcb elimination cluster ion F-(HOR)χ (χ =/> 1) was the major or exclusive reaction channel.The reactions of (CF3)2CD- with these ROH molecules were also examined to observe if D/H exchange occurred in the carbanion-HOR collisions and if deuterium was incorporated into the cluster ion of ROH assisted Elcb elimination.The results from the reactions of (CF3)2CH- and (CF3)2CD-6 with (CH3)3COH (i) the primary product ion was F-(HOC(CH3)3)2; (ii) extensive D/H exchange was observed in (CF3)2CD-, but no deuterium was observed in the fluoride cluster ion product; and (iii) D/H exchange and elimination occurred with the same rate constants> led to the proposal that coordination of (CH3)3COH occurred at two separate sites in the carbanion, C2 for D/H exchange and fluorine of a CF3 group for the ROH assisted Elcb elimination.The results from the collision limited reactions of (CF3)2CHOH and CF3CH2OH are consistent with this mechanistic proposal.The reactions of the carbanions with CH3OH and H2O were too slow to allow for detailed analysis.
Electron transfer as a possible initial step in nucleophilic addition elimination reactions between (radical) anions and carbonyl compounds in the gas phase
Staneke, Paul O.,Ingemann, Steen,Nibbering, Nico M. M.
, p. 179 - 184 (2007/10/03)
The reactions of the HO-, CH3S-, CH2S- and CH2=C(CH3)-CH2- ions with three ketones (CF3COR; R=CH3, CF3, C6H5) and three esters of trifluoroacetic acid (CF3CO2R; R=CH3, C2H5 and C6H5) have been studied with use of Fourier Transform Ion Cyclotron Resonance (FT-ICR) mass spectrometry. All four negative ions react exclusively by proton transfer with CF3COCH3. With the other substrates, the HO- ion reacts by various pathways, such as proton transfer, SN2 substitution, E2 elimination and attack on the carbonyl group. The CH3S- ion is unreactive towards CF3COC6H5 but is able to react by hydride transfer, SN2, E2 and/or carbonyl attack with the remaining neutral species. The CH2S- radical anion reacts by electron transfer to afford stable molecular radical anions of CF3COCF3 and CF3COC6H5, whereas the main reaction with the two esters, CF3CO2CH3 and CF3CO2C2H5, is dissociative electron transfer leading to CF3CO2- and CF3- ions. The CH2=C(CH3)-CH2- anion displays a more complex reactivity pattern involving electron transfer, SN2, E2 as well as attack on the carbonyl group. Direct evidence for the occurrence of electron transfer as the initial step in an overall BAC2 type process has not been obtained for the systems studied. The reaction of the CH2S- ion with CF3CO2C6H5 was observed, however, to yield exclusively a CF3COCHS-. radical anion. Based upon the absence of a BAC2 process in the reaction of CH2S- with the methyl and ethyl esters of trifluoroacetic acid in combination with the facile occurrence of electron transfer from this radical anion, it is suggested that the CF3COCHS-. ion is formed by an initial electron transfer followed by coupling between the CH2S molecule and the CF3CO2C6H5- radical anion and subsequent loss of C6H5OH from the collision complex.
