Acidities in Nonaqueous Solvents

Table 3. Solubilities of the Hydrox ybenzoic Acids in Nonaqueous Solvents, Wt % ...

Hull and Conant in 1927 showed that weak organic bases (ketones and aldehydes) will form salts with perchloric acid in nonaqueous solvents. This results from the ability of perchlonc aad in nonaqueous systems to protonate these weak bases. These early investigators called such a system a superacid. Some authorities believe that any protic acid that is stronger than sulfunc aad (100%) should be typed as a superaad. Based upon this criterion, fluorosulfuric arid and trifluoro-methanesulfonic acid, among others, are so classified. Acidic oxides (silica and silica-aluminai have been used as solid acid catalysts for many years. Within the last few years, solid acid systems of considerably greater strength have been developed and can he classified as solid superacids. 

Complexes such as cis-[Mo(N2)2(PMe2Ph)4 react with protic acids in nonaqueous solvents to give ammonia and hydrazine in yields which depend upon the complex, the solvent, and the acid employed (18, 103, 190, 320), for example, reaction (42). 

In recent years, increasing interest has been attached to the properties of nucleic acids in nonaqueous solvents. It is outside the purview of this article to review all the studies that have so far been carried out with such systems certain observations have been made, however, which bear directly on the interpretation of the behavior of proteins in nonaqueous... 

In nonaqueous solvents, it is possible to react HF to create H2F. Which of these statements follows from this observation (a) HF can act like a strong acid in nonaqueous solvents,... 

Acidities of weak acids in dimethyl sulphoxide solutions. The H-acidity scales 250 Acidity in nonaqueous solvents. Acidity scales in dimethyl sulphoxide solution 251... 

Enthalpies and entropies of activation for the decarboxylation of oxalic, malonic, and acetic acids are listed in Table 1 and are shown separately on the isokinetic plots in Fig. 8. Linear trends are observed for (1) aqueous acetic acid and sodium acetate in the presence of various catalysts (2) aqueous oxalic acid at several pH values (3) oxalic acid in different solvents and (4) malonic acid in different solvents and in aqueous solutions having a different pH. Note that the isokinetic trend for the decarboxylation of malonic acid in aqueous solutions at various pH is identical to that for the reaction in nonaqueous solvents, i.e., there is one isokinetic trend for malonic acid. Moreover, the effect of pH on the activation parameters for the decarboxylation of malonic acid in aqueous solution is minimal. On the other hand, the activation data for the decarboxylation of oxalic acid in aqueous solutions determined by Crossey (1991) do not follow the same isokinetic trend as do the corresponding data for this reaction in other solvents. By contrast, activation data calculated from the rate constants determined by Dinglinger and Schroer (1937) for oxalic acid in water (pH 0.5) fall on the isokinetic trend set by the decarboxylation of oxalic acid in nonaqueous solvents, as well as the rate data determined by Lapidus et al. (1964) in the vapor phase. The cause of the disparity between the isokinetic relationships determined by Crossey (1991) and the remainder of the oxalic acid results requires further investigation. The reaction could have been surface-catalyzed, but this is doubtful because some of the oxalic acid... 

---