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Open Access Anhydrous formic acid and acetic anhydride as solvent or additive in nonaqueous titrations

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The use and importance of formic acid and acetic anhydride (Ac2O) is increasing in nonaqueous acid-base titrations, but their interaction with the solutes is poorly understood. This paper attempts to clarify the effect of the solvents; NMR and spectrophotometric investigations were done to reveal the interactions between some bases and the mentioned solvents. Anhydrous formic acid is a typical protogenic solvent but both the relative permittivity and acidity are higher than those of acetic acid (mostly used in assays of bases). These differences originate from the different chemical structures: liquid acetic acid contains basically cyclic dimers while formic acid forms linear associates. Ac2O is obviously not an acidic but an aprotic (very slightly protophilic) solvent, which supposedly dissociates slightly into acetyl (CH3CO+) and acetate (AcO) ions. In fact, some bases react with Ac2O forming an associate: the Ac+ group is bound to the δ charged atom of the reactant while AcO is associated with the δ+ group at appropriate distance.

Document Type: Research Article

Affiliations: 1: Department of Inorganic and Analytical Chemistry, Eötvös University, P.O. Box 32, Budapest, H-1518, Hungary, Email: 2: Department of Inorganic and Analytical Chemistry, Debrecen University, Debrecen, Hungary 3: Department of Inorganic and Analytical Chemistry, Eötvös University, Budapest, Hungary

Publication date: September 1, 2005

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  • Pharmazie is one of the world's leading pharmaceutical journals. As a peer-reviewed scientific journal, DiePharmazie is regularly indexed in Current Contents/Life Sciences, Excerpta Medica, Analytical Abstracts, International Pharmaceutical Abstracts, Beilstein Current Facts in Chemistry, Chemical Engineering and Biotechnology Abstracts (CEABA) and Science Citation Index.
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