Acid in dipolar aprotic solvents

Reactions of ascorbic acid have been intensively studied in relation to the behavior of this familiar compound in biological systems. Most of the studies treated ascorbic acid as an simple outersphere reducing reagent, until Creutz published an article concerning the complexity of the reaction pathways of ascorbic acid and related radicals. The authors recently demonstrated that the oxidation reactions of ascorbic acid in acidic aqueous solutions are not adiabatic from the volume analysis of the reactions. As the non-adiabaticity of the ascorbate reactions implies the involvement of the proton dissociation and/or ring-closure processes at the rate-determining step, it is expected that Ae reactions of ascorbic acid in dipolar aprotic solvents such as dimethyl sulfoxide (DMSO) are adiabatic. ... 

The success of carbonates depends on the full deprotonation of pronucleophile Nu-H by liberated alkoxide anion. Otherwise, attack of alkoxide on the cationic i7 -allylpalladium(n) complex would afford aUyl ethers, and this is sometimes a side reaction. Allylation of nucleophiles by allylic carbonates is customarily carried out in more or less polar aprotic solvents (THF, DMSO, DMF), and less frequently in dichloromethane, toluene, and even in water. The orders of acidity in dipolar aprotic solvents and in water are quite different, and this should be taken into account to know the position of the acid-base equilibrium. Lists of pA values in DMSO are availablc. - Orders of acidities in THF and in DMSO are probably not different. Examples of pA (DMSO) are MeCOCH2COOEt (14.4), CH2(COOEt)2 (16.4), PhOH (18.0), methanol (29.0), aniline (30.6), water (31.2), and ammonia (estimated 40). 

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