[ad_1]
The selection of the impact parameter is fundamental to the result of the chemical reaction, as visualized here from the experiments. At the zero impact parameter, the top reaction shows a reproducible formation of a bound pair of CF2 molecules on the surface of the copper. In the second case, at the bottom, collision with a slightly higher impact parameter (3.6 Angstroms, rather than zero), the products indicated on the right of the photo are always very far apart, chemically linked separately to the underlying metal. It is also a chemical reaction, but showing a different reaction pattern with the metal. It can be seen that the impact parameter determines the reaction path. This has not been shown before because it was not possible to select the impact parameter. Credit: Kelvin Anggara & Lydie Leung / University of Toronto
Scientists at the University of Toronto have found a way to select the result of a chemical reaction using an elusive and long-sought factor, known as the "parameter of impact."
The University of Toronto chemistry team, led by Nobel laureate researcher John Polanyi, has found a way to select the impact parameter or safety distance by which a reagent molecule misses a target molecule thus modifying the products of the chemical reaction. The results are published today in Progress of science.
"Chemists are constantly launching molecules on other molecules in the hope of creating something new," says Polanyi, a professor in the Department of Chemistry at the University of Toronto. "In this study, we found a way to control the outcome by targeting a molecule projectile at a target molecule, with a precision of a small fraction of the target molecule's diameter."
Molecular dynamics in chemistry seem much like a game of billiards. Just as a billiard player sends the incoming ball to the target, chemists throw one molecule to another to produce a chemical reaction. However, this can be done, this is now clear, either by chance as has been the norm, or by design, as shown by the new work possible.
Previously, the randomness inherent in molecular motions prevented chemists from directing their projectile molecules at chemical targets, as do billiard players. Instead, they were forced to play pool with blindfolded eyes.
"Over the years, chemists have become very good at blindfolding billiards, using sticky balls and throwing them with strength or weakness," Polanyi said. "But we found a way to remove the blindfold and aim each shot."
The researchers did this by depositing molecules on a metal crystal and then applying a small current from an atomically sharp metal tip to one of the molecules. This addition of energy caused the projection of a "projectile" molecule on the surface in a straight line, along one of the rail-shaped ridges on the metallic crystal towards a "target" molecule near present on the crystal, thus missing a controlled amount.
Different missing distances, called "impact parameters", have been shown in a reproducible way to give different results, that is to say different reaction models.
"The underlying crystal surface is our pool table," said Kelvin Anggara, a postdoctoral researcher at Polanyi's research group and lead author of the study. "By taking advantage of the grooves nature has conveniently dug out of the surface of the crystals, we have discovered that we can guide the traveling molecular projectile so that it reaches the target, directly or indirectly, when it reaches the target. a collision that would have missed the target, so, as in the case of billiards, we can control the outcome of the molecular collision. "
Selection of Missing Distance or Impact Parameter in Reagent Molecule Collisions has so far been described as "Defended Fruit of Reaction Dynamics" by Dudley R. Herschbach, Harvard University Professor , with whom Polanyi shared the 1986 Nobel Prize for chemistry with Yuan T. Lee While the trio's discoveries allowed chemists to deduce many of the forces involved in a chemical reaction, the impact parameter challenged the direct control.
This is true even under the well-known conditions of "crossed molecular beams". It is often forgotten that even if the beams of this elegant method are directed toward one another, the molecules are not. Now the individual molecules can be directed against each other very precisely.
"We believe that it is a major step forward in the control of chemical reactions," said Anggara, who conducted the study with Polanyi, associate researcher Lydie Leung and Dr. Graduate student Matthew Timm.
Explore further:
Chemists discover a way to control catalytic reactions
More information:
"Approach the forbidden fruit of the dynamics of the reaction: orient the reagent on selected impact parameters" Progress of science (2018). DOI: 10.1126 / sciadv.aau2821, http://advances.sciencemag.org/content/4/10/eaau2821
Source link
