Acid-Base Titrations in Nonaqueous Solvents and Solvent Mixtures

Theoretical problems associated with the use of acetic anhydride as a co-solvent for the non-aqueous titration of hydrohalides of organic bases and quaternary ammonium salts

“…(4)- (6)). Our findings are in agreement with statements in earlier papers [6][7][16][17][18] about the behaviour of acetic anhydride which has been characterized as an aprotic and very slightly protophilic solvent that is able to dissociate to acetyl and acetate ions. By shifting this equilibrium with adding perchloric acid to the solvent, in situ formation of acetyl perchlorate takes place which is as a matter of fact the titrating agent of very weak bases as well as of amine hydrohalides and quaternary ammonium halides.…”

“…In the majority of papers from the very early literature up to the present time [6,[13][14][15][16][17][18] this is attributed to the reaction of the halogenide ion with acetic anhydride to form acetyl halides and titratable free acetate ion (see Eqs. (1) and (2)).…”

Introduction to the Solid State – Physical Properties and Processes

“…Database computer programs may be used to assist but, to be on the safe side, experimental pK A -determinations should be made by acid-base titrations or NMR analysis (Kubal et al 1994). It should be noted that pK A -values, which are usually measured in water solutions, can also be determined in nonaqueous solvents, wherein they will take different values (Barcza and Buvári-Barcza 2003).…”

Prediction of acid pKa values in the solvent acetone based on COSMO‐RS

“…While pK a determination is nowadays standard in aqueous solution due to a broad variety of well-established experimental techniques for the solvent water, 7 the situation is very different in non-aqueous solution. 8,9 Especially for aprotic organic solvents, the acidity of a compound is usually severely reduced since an aprotic solvent cannot stabilize the corresponding base effectively due to its inherent lack of H-bond donation, which largely hinders the dissociation event. The resulting extremely low acid dissociation constants in combination with other complications such as low solubilities challenge the accuracy of experimental methods.…”