Chemists advance ability to control chemical reactions

The new way to select the outcome of the chemical reaction by employing an elusive and long-sought factor known as the 'impact parameter'

Chemists advance ability to control chemical reactions

Chemical process and data logging

A chemical reaction is a process that moves the chemical change of one set of chemical substances into another. Classically, chemical reactions involve changes in which the position of electrons in the formation and breaking of the chemical bond between the atoms is included, in which there is no change in the present elements. Differences in parameters like temperature, pressure, the rate of reaction, pH etc. can have a dramatic effect on the quality of the chemical process. Being able to control and data log variables such as these and analyze other parameters such as turbidity, reaction power, enthalpy change etc, is extremely valuable to understanding a chemical process. The role of process chemist is to produce an efficient production process and manage the transfer of that chemical process from laboratory scale to manufacturing. Important considerations include safety, cost, timing accuracy, environmental impact, reproduction and the purity of the final compound.

The fascinating advances in single atom/molecule manipulation with a scanning tunneling microscope tip allow scientists to fabricate atomic-scale structures or to probe chemical and physical properties of matters at an atomic level. These achievements open up entirely new opportunities in nanochemistry and nano chemical technology.

The new way to control chemical reactions

Molecular mobility in chemistry is like a billiards game. A chemist releases one molecule to another to produce a chemical reaction. However, this can be done, it is now clear, either as a chance by standard or design because new work is possible. In the past, Scientists used electric currents to control chemical reactions in a breakthrough that could have implications for how chemicals are made in the future. Recently scientists at the University of Toronto have found a way to select the outcome of the chemical reaction by employing an elusive and long-sought factor known as the 'impact parameter'. The team of the University of Toronto chemists, led by Nobel Prize-winning researcher John. C  Polanyi, have found a means to select the impact parameter or miss-distance by which a reagent molecule misses a target molecule, thereby altering the products of the chemical reaction. The selection of the impact parameter is fundamental to the outcome of the chemical reaction. It shows a different pattern of reaction with the metal. The effect parameter is seen to determine the course of the interaction. This has not been demonstrated before because the effect parameter could not be determined.

John C. Polanyi, University Professor in the Department of Chemistry at the University of Toronto, said in a statement, "Chemists toss molecules at other molecules all the time in hopes of making something new.  In this study, we found a way to control the results by aiming the projectile molecules at the target molecule with a precision that is a small fraction of the diameter of the target molecule. Over the years, chemists have become very good at playing billiards blindfolded, using sticky balls and throwing them vigorously or weakly. But we got a way to overcome the darkness and target each shot."

The scientists achieved this by depositing molecules on a metal crystal, then applying a small current from an atomically sharp metal tip to one of the molecules. As a result of the increase in energy, a 'projectile' molecule in the straight line with a railway-like mountain on the metal crystal has been left on the crystal to the "target" molecule and it has been lost with control. Different distorted spaces, called "impact parameters", are repeated to give different results, i.e., different types of interactions.

The selection of miss-distance or impact parameters in a collision between reagent molecules is called ""forbidden fruit of reaction dynamics" till now. 

Kelvin Anggara, a postdoctoral fellow in Polanyi's research group and a lead author of the study explained "The underlying crystalline surface is our billiard table. By taking advantage of the grooves that nature has conveniently scored across the surface of crystals, we found we could guide the traveling molecular projectile so that it hit the target either head-on or in a glancing collision that missed the target by the desired amount. In this way, billiards, we can control the outcome of molecular collisions. This is true even in the famous well-controlled conditions of "cross molecular beam." It is frequently overlooked that though the beams in this elegant method are aimed at one another, the molecules are not. Now the goal of individual molecules can be done for each other, absolutely fine. We believe that this is a major step in the control of chemical reactions.

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Journal reference: Science Advances, 2018 DOI: 10.1126/sciadv.aau2821