FeIII -Based Eutectic Mixtures as Multi-task and Reusable Reaction Media for Efficient and Selective Conversion of Alkynes into Carbonyl Compounds

An efficient, simple and general protocol for the selective hydration of terminal alkynes into the corresponding methyl ketones has been developed by using a cheap, easy-to-synthesise and sustainable FeIII -based eutectic mixture [FeCl3  ⋅ 6H2 O/Gly (3 : 1)] as both promoter and solvent for the hydration reaction, working: i) under mild (45 °C) and bench-type reaction conditions (air); and ii) in the absence of ligands, co-catalysts, co-solvents or toxic, non-abundant and expensive noble transition metals (Au, Ru, Pd). When the final methyl ketones are solid/insoluble in the eutectic mixture, the hydration reaction takes place in 30 min, and the obtained methyl ketones can be isolated by simply decanting the liquid FeIII -DES, allowing the direct isolation of the desired ketones without VOC solvents. By using this straightforward and simple isolation protocol, we have been able to recycle the FeIII -based eutectic mixture system up to eight consecutive times. Furthermore, the FeIII -eutectic mixture is able to promote the selective and efficient formal oxidation of internal alkynes into 1,2-diketones, with the possibility of recycling this system up to three consecutive times. Preliminary investigations into a possible mechanism for the oxidation of the internal alkynes seem to indicate that it proceeds through the formation of the corresponding methyl ketones and α-chloroketones.

Complexation effect of copper(ii) with HEDP supported by activated carbon and influence on acetylene hydration

The effect of copper(ii) complexation with HEDP on an AC support was evaluated for acetylene hydration.

A density functional theory exploration on the Zn catalyst for acetylene hydration

The acetylene hydration method to produce acetaldehyde has been widely used for over 130 years; however, a detailed molecular-level understanding of the reaction mechanism is still lacking. In the present work, we systematically investigated the mechanisms of such reactions on ZnCl₂, Zn(OH) Cl, and Zn(OH)₂ catalysts through density functional theory (DFT) methods. The Fukui function, condensed Fukui function, and Hirshfeld charges enabled us to predict the active sites of the catalysts and acquire electron transfer information. From these data, we found that catalysts bearing hydroxyl groups exhibited relatively low adsorption performances compared with catalysts without this functionality. The calculations demonstrated that the three studied catalysts had three distinct reaction paths. For the Zn(OH)Cl and Zn(OH)₂ catalysts, the reaction took place through a one-shift H₂O molecule transfer route, avoiding higher energy barrier pathways. Interestingly, we found that the energy required for breaking the O-H bond in water determined the activation energy of the studied catalytic reactions. The activation barrier increased in the order Zn(OH)Cl ≈ Zn(OH)₂ < ZnCl₂. This trend suggests that Zn(OH)Cl and Zn(OH)₂ are promising catalysts for the hydration of acetylene. Graphical abstract.

Ketone Hydrogenation by Using ZnO-Cu(OH)Cl/MCM-41 with a Splash of Water: An Environmentally Benign Approach

MCM-41-supported ZnO-Cu(OH)Cl nanoparticles were synthesized via an incipient wetness impregnation technique using zinc chloride and copper chloride salts as well as water at room temperature. The catalyst was characterized by powder X-ray diffraction (PXRD), infrared spectroscopy (IR), and TGA, whereas surface and morphological studies were performed by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The above studies revealed the incorporation of metal species into the pores of MCM-41, leading to a decrease in surface area of the nanoparticles that was found to be 239.079 m² /g. The substituents attached to the ketone determine the rate of the reaction, and the utilization of the green solvent 'water' astonishingly completes the hydrogenation reaction in 45 minutes at 40 °C with 100% conversion and 100% selectivity as analyzed by gas chromatography-mass spectrometry. Hence, ZnO-Cu(OH)Cl/MCM-41 nanoparticles with 2.46 wt% zinc and 6.39 wt% copper were demonstrated as an active catalyst for the reduction of ketones without using any gaseous hydrogen source making it highly efficient as well as environmentally and economically benign.