JDJCSET | Sigma Xi Poster Competition

Title

Breaking Covalent Bonds With a Mortar and a Pestle

Academic Level at Time of Presentation

Junior

Major

Chemistry

2nd Student Academic Level at Time of Presentation

Junior

2nd Student Major

Chemistry

List all Project Mentors & Advisor(s)

Sebastian Jezowski, PhD

Presentation Format

Poster Presentation

Abstract/Description

Effects of mechanical energy in certain physico-chemical processes were observed and applied in practice as early as in the era of Aristotle. One example is mercury extracted by mechanical treatment of cinnabar in a brass mortar equipped with a pestle in the presence of vinegar. Mechanical force deforms reactants along a specific direction and alters the shape of potential energy surfaces. This in turn results in the formation of reaction products that cannot be normally generated with the application of either heat or light. In order to break a typical C-C covalent bond present in most molecular compounds, one needs to apply pressure on the order of 100 kbar (or 10 GPa). Directed forces can be induced in several ways, for instance by generating shock-waves, with scanning probe microscopy tips or by bubble cavitation.

A new class of mechanophoric system, bis-anthracene, BA, and its photoisomer, PI, has been shown to respond reversibly to a mild, hydrostatic (below 1 GPa) pressure induced in a Diamond Anvil Cell. By performing absorption spectroscopy measurements we were able to demonstrate that shear deformation in the form of mechanical grinding also induces similar changes leading to the permanent deformation of a covalent C-to-C bond in PI. This transformation induced by anisotropic force is also coupled with rehybridization and results in the formation of a higher volume product (BA). In a separate experiment we have also synthesized selectively deuterated BA (BA-d) and performed crystal X-ray analysis.

Spring Scholars Week 2018 Event

Sigma Xi Poster Competition

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Breaking Covalent Bonds With a Mortar and a Pestle

Effects of mechanical energy in certain physico-chemical processes were observed and applied in practice as early as in the era of Aristotle. One example is mercury extracted by mechanical treatment of cinnabar in a brass mortar equipped with a pestle in the presence of vinegar. Mechanical force deforms reactants along a specific direction and alters the shape of potential energy surfaces. This in turn results in the formation of reaction products that cannot be normally generated with the application of either heat or light. In order to break a typical C-C covalent bond present in most molecular compounds, one needs to apply pressure on the order of 100 kbar (or 10 GPa). Directed forces can be induced in several ways, for instance by generating shock-waves, with scanning probe microscopy tips or by bubble cavitation.

A new class of mechanophoric system, bis-anthracene, BA, and its photoisomer, PI, has been shown to respond reversibly to a mild, hydrostatic (below 1 GPa) pressure induced in a Diamond Anvil Cell. By performing absorption spectroscopy measurements we were able to demonstrate that shear deformation in the form of mechanical grinding also induces similar changes leading to the permanent deformation of a covalent C-to-C bond in PI. This transformation induced by anisotropic force is also coupled with rehybridization and results in the formation of a higher volume product (BA). In a separate experiment we have also synthesized selectively deuterated BA (BA-d) and performed crystal X-ray analysis.