AsianScientist (Jul. 14, 2016) – Two researchers at Japan’s Okinawa Institute of Science and Technology Graduate University (OIST) have found a single chemical procedure that can create industrial-use alcohol and esters without generating any waste and while avoiding the use of harmful reagents. Their findings were published in ACS Catalysis.
Alcohols have numerous medical and industrial applications, such as drugs and antifreeze. Esters, a class of organic compounds, are utilized by the food and cosmetics industries to add specific flavors to food or perfumes. The processes to create alcohols and esters, however, have typically been carried out under harsh conditions, with high temperatures and caustic reagents that leave behind pollutant waste.
Dr. Abhishek Dubey and Dr. Eugene Khaskin from the OIST Coordination Chemistry and Catalysis Unit started with a known concept in organic chemistry called metathesis, where molecules are scrambled, and wondered whether it could be applied to esters. Eventually, they hit on the right formula: their reaction breaks and reforms the connections between the core of an ester and its peripheral fragments, re-arranging the fragments in four different ways.
“According to this rearrangement, we should get four possible products, and that’s what we see,” Khaskin said. “We start with one ester, and we end up with four: one that is the same as the ester we started with, and the three others that are chemically possible.”
Depending on their structure, esters have very different smells. As each one of the new products has a specific molecular arrangement, their smell is completely different. The smells also change quite dramatically depending on how far the reaction has progressed.
Khaskin said that the scent of the resulting mixture depends on its components, and he would often get a “pleasant, fruity surprise” when he stopped the reaction and opened up the vial.
“Usually in chemistry, unlike back home in the kitchen, it’s not a good idea to smell what you’re cooking, but this is one of the perks of working with esters,” Khaskin commented.
The process is also less complicated than previous ones.
“Our process has one step: you find an ester that can rearrange into the esters you need, you just put that starting ester in the flask, add a catalyst, heat everything at the appropriate temperature, and after few hours, it’s done,” Dubey explained.
While the esters created during this process are known, the method has the potential of creating new molecules and new mixtures.
Furthermore, slightly tweaking the reaction conditions by adding ethanol to the same reaction transforms the starting ester into an alcohol. Creating alcohols from esters is usually a difficult process that involves high-pressure hydrogen and specialized equipment, but the new process does not require any of this, and is therefore safer and easy to perform.
The scientists believe that these processes represent an economical, green-chemistry alternative to previous synthetic routes.
The article can be found at: Dubey & Khaskin (2016) Catalytic Ester Metathesis Reaction and its Application to Transfer Hydrogenation of Esters.
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Source: Okinawa Institute of Science and Technology Graduate University ; Photo: Shutterstock.
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