RUDN chemists have proven the effectiveness of metal complexes to catalyse the production of cyanohydrin, important substances for the chemical industry. Chemists managed to achieve 96.3% of the reaction efficiency. The results are published in Polyhedron.
Newswise — Cyanohydrins are organic substances with nitrile and hydroxyl groups that are used in industrial chemistry as raw materials for polymers, acids, alcohols, and other compounds. One of the ways to obtain cyanohydrins is the addition of prussic acid to aldehydes. Without catalysts, this reaction is possible, but gives a small yield of the product - about 20%. To create existing catalysts, expensive and dangerous reagents are required, and the reaction itself takes time. RUDN chemists together with colleagues have shown that complexes of some metals, the synthesis of which takes place under mild conditions, can be effective catalysts for this process.
"Despite the wide variety of catalytic systems for cyanhydrin production, most of them have significant disadvantages — the use of harmful and expensive components and solvents, long reaction time, low yields, etc. Therefore, the development of a practical catalytic system for the efficient production of cyanhydrins from aldehydes under mild conditions remains a difficult task. We decided to test (investigate) several relatively easy-to-prepare and inexpensive metal complexes as potential catalysts," said Evgenia Nikitina, PhD, Associate Professor of the Department of Organic Chemistry of RUDN.
For catalytic reactions chemists chose four complexes of cadmium, mercury, zinc and lanthanum. The same ligand was used to synthesize these complexes. Solvent, aldehyde and trimethylsilyl cyanide were added to the test tube with the catalyst, then the solution was mixed. The course of the reaction was monitored using thin-layer chromatography. After the reaction was completed, the RUDN chemists analysed the resulting product using NMR spectroscopy.
The most effective catalyst was a complex with lanthanum. In its presence, the reaction proceeded for six hours at room temperature. The output of the final product was almost perfect - 96.3%. Chemists also studied which components of the lanthanum catalyst are responsible for its effectiveness and came to the conclusion that one of the most important factors are non-covalent interactions and donor-acceptor bonds. The first - weaker - determine the shape and stability of the molecule, the second - stronger - hold its very structure.
"Compared to other coordination catalysts for similar aldehyde conversion, the lanthanum-based catalyst has better performance. The yield of the product is up to 96.3% in six hours at room temperature. Moreover, the previously studied catalytic systems based on metal complexes require additives, a longer reaction time, a larger amount of catalyst and higher temperatures, while the yield of cyanohydrins is usually lower," – said Fedor Zubkov, PhD, Associate Professor of the Department of Organic Chemistry of the RUDN University.
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