Journal ArticleDOI
Equilibrium Acidities in Dimethyl Sulfoxide Solution
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The first acidity scale to be established in a pure solvent other than water was the result of the pioneering work of Conant, Wheland, and McEwen in ether or ben~ene.Abstract:
The first acidity scale to be established in a pure solvent other than water was the result of the pioneering work of Conant, Wheland, and McEwen in ether or ben~ene .~ During the past 20 years an ion-pair acidity scale covering an \"effective pKa rangefrom about 15 to 40 has been developed in cyclohexylamine (CHA),6 and similar studies in other low-dielectric-constant solvents including 1,2-dimethoxyethane (DME)7a and tetrahydrofuran (THF)7b*c have been carried out. A more limited ion-pair acidity scale has been developed in liquid NH,.7d Also, during this period, acidity scales have been established in the polar non-hydrogenbond-donor (NHBD) solvents dimethyl sulfoxide (Me$0)8 and N-methylpyrrolidin-2-one (NMP)? which have relatively high dielectric constants. The pK,'s measured in these solvents differ from ion-pair pK,'s in that they are absolute, in the sense that they are based on Me2S0 and NMP as the standard states, which allows direct comparisons to be made with H20 and gas-phase pK,'s. A truly absolute acidity scale has been established in the gas phase, which, for the first time, provides intrinsic measures of structural effects free of solvent effects.1° Our purpose in this Account is (a) to discuss briefly acidities in various solvent media, (b) to present a table of representative equilibrium acidity constants in M e 8 0 solution, and (c) to illustrate ways in which these pK, data can be used. In an accompanying Account we compare acidities in Me2S0 solution with intrinsic gas-phase acidities and discuss some of the insights into solvation effects provided thereby. Acidities in H 2 0 and Me2S0. It is important to recognize that pKa values are solvent dependent. Theread more
Citations
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Small-molecule H-bond donors in asymmetric catalysis.
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References
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Journal ArticleDOI
Equilibrium acidities of carbon acids. VI. Establishment of an absolute scale of acidities in dimethyl sulfoxide solution
Walter S. Matthews,Joseph E. Bares,John E. Bartmess,Frederick G. Bordwell,Frederick J. Cornforth,George E. Drucker,Zafra Margolin,Robert J. McCallum,Gregory J. Mccollum,Noel R. Vanier +9 more
TL;DR: An accurate spectrophotometric method of determining relative equilibrium acidities of carbon acids in DMSO has been developed as discussed by the authors, and the pK of fluorene, formerly arbitrarily taken as 20.5, has been raised to an absolute value of 22.6.
Book
Electron transfer reactions in organic chemistry
TL;DR: The electron transfer reaction between two species of different chemical composition has been studied extensively in the literature as discussed by the authors, where electron transfer reactions constitute the basis of theoretical treatments of electron transfer and self-exchange reactions.
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