49745-25-7Relevant articles and documents
Nucleophilic Reactions of F3C- at sp2 and sp3 Carbon in the Gas Phase. Characterization of Carbonyl Addition Adducts
McDonald, Richard N.,Chowdhury, A. Kasem
, p. 7267 - 7271 (1983)
The reactions of F3C- with CH3Br and CH3Cl established the medium kinetic nucleophilicity of F3C- on Bohme's reactivity scale for gas-phase SN2 reactions.The reactions of F3C- with (CH3)2C=O and CH3CO2CH3 proceeded by competitive bimolecular H+ transfer and termolecular carbonyl addition giving the corresponding adducts anions m/z 127 and 143, respectivaly.F3C- reacted with esters C6H5CO2CH3, CF3CO2CH3, and (CH3O)2C=O both by SN2 displacement forming the corresponding carboxylate anions and by carbonyl addition yielding the adduct anions; with CF3CO2C2H5 and CF3CO2C(CH3)3, the competitive bimolecular reaction channel involved E2 elimination giving CF3CO2-.The major reaction channel of F3C- with HCO2CH3 was the Riveros reaction that produced the series of cluster ions F3C-(HOCH3), F3C-(HOCH3)2, CH3O-(HOCH3), and CH3O-(HOCH3)2, along with a minor amount of carbonyl addition.The fast termolecular reaction of F3C- with (CF3)2C=O exclusively formed the adduct (CF3)3CO- (m/z 235) which was characterized as the bound, tetrahedral structure by bracketing its proton affinity.The reaction of F3C- with CO2 giving CF3CO2- was established as a termolecular process when the "apparent" bimolecular rate constant was shown to be PHe dependent.These results demonstrate unequivocally that the reactions of gas-phase nucleophiles with the carbonyl group of ketones and esters proceed by addition yielding the corresponding adduct oxyanions which is analogous to the related process in the condensed phase.
Model Studies of Coenzyme B12 Dependent Diol Dehydratase. 2. A Kinetic and Mechanistic Study Focusing upon the Cobalt Participation or Nonparticipation Question
Finke, Richard G.,Schiraldi, David A.
, p. 7605 - 7617 (2007/10/02)
In the preceding paper 1 model analogues of the putative diol dehydratase intermediates -CH(OH)CH2OH (1) and -CH2CHO (2) ( = coenzyme B12) were synthesized and characterized by using the Co B12 model system, with the unstable, postulated intermediate 1 being prepared in a carbonate-protected form (3), .The CH3O-/CH3OH catalyzed deprotection of 3 and subsequent formation of 100percent CoIICl, 95percent CH3CHO, and 50percent each of CH3OCO2CH3 and CH3OCO2- were also described, as were experiments suggesting the noninvolvement of OHCCH2CoCl in this reaction.In the present manuscript, a kinetic and mechanistic study of this methanolysis reaction , 3 + CH3O-/CH3OH, is presented and evidence for the formation of α-hydroxy, Co-CH(OH)CH2OR, complexes such as 1 is provided.Nitroxide radical trapping and added 1,5,6-trimethylbenzimidazole experiments are described, and the possible intermediates consistent with these experiments are presented.Cyclic voltammetry, literature precedent, and Meyerstein's related observations with coenzyme B12 are provided as interpretation for the CH3CHO-inhibiting, but Co(I)- and HOCH2CHO-producing, side reaction induced by the added axial ligand.Evidence against cobalt participation pathways involving Co(I)- and Co(III) is described, and additional mechanistic experiments probing the apparent, nonformation of Co-CH2CHO (6) are presented.The results obtained (1) provide good evidence against cobalt participation in the rearrangement step, (2) rule out the often cited, but unverified, Co(III) ?-complex mechanism, (3) demonstrate that base-on cobalt participation is not only unnecessary, it introduces a CH3CHO-inhibiting side reaction, and (4) provide evidence that, when combined with literature stereochemical and other studies, suggest that it is the protein and not the cofactor which has the more significant role in diol dehydratase.
