915775-87-0Relevant academic research and scientific papers
Effect of Solvation on the Nucleophilic Reaction of Stable Carbanions with Diaryl Disulfides
Gilbert, H. F.
, p. 7059 - 7065 (1980)
Stable carbanions react with diaryl disulfides in aqueous solution by direct displacement (SN2) reaction to yield an arylthiol anion and the corresponding sulfide as products.The reaction of 1,3-dicarbonyl carbanions with 5,5'-dithiobis(2-nitrobenzoic acid) is characterized by Broensted βC value of 0.5.Nitroalkane carbanions react 102-104 slower than 1,3-dicarbonyl carbanions of the same pK and are correlated by a Broensted βC of 0.95.The second-order rate constants for the reaction of nitroalkane carbanions increase by factors of 104-106 as the solvent is changed from water to dimethyl sulfoxide.Smaller increases are observed in the rate constants for reaction of 2,4-pentadienone carbanion (102) and malonitrile carbanion (100.6) with the same sulfide.A linear correlation is found between log (kMe2SO4/kHOH) and the increase in pK for the carbon acid ionization on changing the solvent from water to dimethyl sulfoxide.The effect is attributed to large differences in ground-state carbanion solvation which are reduced or absent in the transition state.Parallels are drawn between the nucleophilic reaction of stable carbanions with diaryl disulfides and proton-transfer reactions of the same carbanions.
