Vibrations can be used to design better catalysts, scientists say


SigmanMilo

Scientists at the University of Utah, US, have found a new way of predicting chemical reactions through vibrations in chemical bonds.

The new method is claimed to help design better catalysts for accelerating reactions, to manufacture medicines, industrial products and new materials with fewer byproducts and less waste.

Catalysts are substances that increase the rate of reaction between other chemicals without changing the catalyst itself.

University of Utah chemistry professor and senior author of the study Matt Sigman said: "The vibrations alone are not adequate, but combined with other classical techniques in physical organic chemistry, we are able to predict how reactions can occur.

"It streamlines the process of designing molecules for uses in new drugs, industrial chemicals and new materials."

Financed by the National Science Foundation, the research was conducted by Anat Milo, Sigman and Elizabeth Bess, a chemistry student, at the university.

As part of the research, the scientists performed three case studies, each featuring a different class of chemicals reacting with one another.

Through computer simulations they predicted the outcome of the reactions, and then experimentally verified the results in the laboratory.

The first case study involved reaction of bisphenols and acetic anhydride with peptide as a catalyst.

To predict whether the resulting molecule would be 'left-handed' or 'right-handed,' the chemists simulated bond vibrations on different bisphenols.

Milo said: "We managed to predict the handedness of the molecules accurately."

"As part of the research, the scientists performed three case studies, each featuring a different class of chemicals reacting with one another."

In the second case study, the catalyst was used to convert a double carbon-carbon bond to a single carbon-carbon bond in diarylalkene to predict the 'handedness' of chemicals.

The third case study involved a Heck reaction to identify whether a catalyst reacts with one side or the other side of a double carbon-carbon bond.

According to Sigman, in order to use the new technique for practical purposes one would compute infrared vibrations for a specific class of molecules.

Sigman said: "You then take a handful of those molecules and you run the reaction and get the results.

"Then you take the infrared vibrations you think are important and determine the relationship between those vibrations and the reaction results.

"The resulting mathematical equation allows you to make new predictions about how other chemicals in the class will react."

Chemical bonds help in binding together atoms in the molecules, and the bonds are not static.

Since they vibrate, they reflect changes in distance between atoms in the molecule.


Image: Chemists at the University of Utah identified a new method using vibrations in chemical bonds to improve predictions of how chemicals react. Photo: courtesy of Lee J. Siegel / University of Utah.

Energy link