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The mechanisms of a tetrasubstituted imidazole [2‐(2,4,5‐triphenyl‐1 H‐imidazol‐1‐yl)ethan‐1‐ol] synthesis from benzil, benzaldehyde, ammonium acetate, and ethanolamine in [Et 2 NH 2 ][HSO 4 ] ionic liquid (IL) are studied computationally. The effects of the presence of the cationic and anionic components of the IL on transition states and intermediate structures, acting as a solvent versus as a catalyst, are determined. In IL‐free medium, carbonyl hydroxylation when using a nucleophile (ammonia) proceeds with a Gibbs free energy (Δ G  ≠ ) barrier of 49.4 kcal mol −1 . Cationic and anionic hydrogen‐bond solute–solvent interactions with the IL decrease the barrier to 35.8 kcal mol −1 . [Et 2 NH 2 ][HSO 4 ] incorporation in the reaction changes the nature of the transition states and decreases the energy barriers dramatically, creating a catalytic effect. For example, carbonyl hydroxylation proceeds via two transition states, first proton donation to the carbonyl (Δ G  ≠ =9.2 kcal mol −1 ) from [Et 2 NH 2 ] + , and then deprotonation of ammonia (Δ G  ≠ =14.3) via Et 2 NH. Likewise, incorporation of the anion component [HSO 4 ] −  of the IL gives comparable activation energies along the same reaction route and the lowest transition state for the product formation step. We propose a dual catalytic IL effect for the mechanism of imidazole formation. The computations demonstrate a clear distinction between IL solvent effects on the reaction and IL catalysis.

Ionic Liquid Solvation versus Catalysis: Computational Insight from a Multisubstituted Imidazole Synthesis in [Et 2 NH 2 ][HSO 4 ]