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Solvents as acids and bases

المؤلف:  Peter Atkins, Tina Overton, Jonathan Rourke, Mark Weller, and Fraser Armstrong

المصدر:  Shriver and Atkins Inorganic Chemistry ,5th E

الجزء والصفحة:  141

2025-08-28

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Solvents as acids and bases

The solvent system definition of acids and bases allows solutes to be defined as acids and bases by considering the autoionization products of the solvent. Most solvents are also either electron pair acceptors or donors and hence are either Lewis acids or bases. The chemical consequences of solvent acidity and basicity are considerable, as they help to account for the differences between reactions in aqueous and nonaqueous media. It follows that a displacement reaction often occurs when a solute dissolves in a solvent, and that the subsequent reactions of the solution are also usually either displacements or metatheses. For example, when antimony pentafluoride dissolves in bromine trifluoride, the following displacement reaction occurs:

In the reaction, the strong Lewis acid SbF₅ abstracts F^– from BrF₃. A more familiar example of the solvent as participant in a reaction is in Brønsted theory. In this theory, the acid (H) is always regarded as complexed with the solvent, as in H₃O if the solvent is water, and reactions are treated as the transfer of the acid, the proton, from a basic solvent molecule to another base. Only the saturated hydrocarbons among common solvents lack significant Lewis acid or base character.