Leveling effect

Strong bases are leveling solvents for acids, weak bases are differentiating solvents for acids. In a leveling solvent, many acids are completely dissociated and are thus of the same strength. All acids tend to become indistinguishable in strength when dissolved in strongly basic solvents owing to the greater affinity of strong bases for protons. This is called the leveling effect. In a differentiating solvent on the other hand, various acids dissociate to different degrees and thus have different strengths. For example, anhydrous acetic acid (CH3COOH) as solvent is a weaker proton acceptor than water. Strong aqueous acids such as hydrochloric acid and perchloric acid are only partly dissociated in anhydrous acetic acid and their strengths are unequal; in fact perchloric acid is about 5000 times stronger than hydrochloric acid in this solvent. ==Types of solvent on the basis of proton interaction==

On the basis of proton interaction, solvents are of four types, (i) Protophilic solvents: Solvents which have greater tendency to accept protons, i.e., water, alcohol, liquid ammonia, etc. (ii) Protogenic solvents: Solvents which have the tendency to produce protons, i.e., water, liquid hydrogen chloride, glacial acetic acid, etc. (iii) Amphiprotic solvents: Solvents which act both as protophilic or protogenic, e.g., water, liquid ammonia, ethyl alcohol, etc. (iv) Aprotic solvents: Solvents which neither donate nor accept protons, e.g., benzene, carbon tetrachloride, carbon disulfide, etc. HCl acts as a strong acid in H2O, an even stronger acid in NH3, a weak acid in CH3COOH, neutral in C6H6 and a weak base in HF. NaHSO3 acts as a weak acid in DMSO, a strong acid in NH3, a weak base in glacial acetic acid, and a strong base in sulfuric acid. ==References==