| Abstract
| - Direct ring hydroxylation of aromatics, namely, anisole, toluene, and benzylchloride, using TS-1 catalyst, aMFI-type titanium silicate molecular sieve, dilute H2O2 as oxidizing agent, and water as reaction medium,was investigated under solid−liquid−liquid (SLL)-type triphase conditions. The aim was to study the relativeinfluence of commonly used organic solvents, under solid−liquid (SL)-type biphase reaction conditions, ascompared to that of water, on the conversion and product selectivity. Under solvent-free triphase conditions,the ring hydroxylation of anisole, toluene, and benzylchloride leads to significant enhancement in the conversion,turn-over frequency, and para-selectivity. However, in the case of benzyl chloride, no ring hydroxylationtook place under biphase conditions (using acetone as solvent) contrary to significant ring hydroxylation (ca.60% H2O2 efficiency) under triphase aqueous medium conditions. The simple product recovery (phaseseparation of organic and aqueous layers) and use of water as reaction medium are other advantages. SinceTS-1 is relatively hydrophobic, the reaction is hindered in the presence of organic solvents as they competefavorably with the substrate for diffusion inside the TS-1 channels. However, in the presence of water, theorganic substrate competes favorably with water, leading to increased conversion and para-selectivity.
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