![]() ![]() “When light strikes a molecule and prompts a proton transfer reaction, it may seem that only a bare proton shifts its position,” Wu said, “but what really is happening is an enormous change in the electronic structure of the whole molecule. Proton Transfer Reactions: An Escape Route for Photoexcited Molecules to Get Rid of Antiaromaticity A proton transfer reaction is one way of doing so. Once this happens, the key driving force is returning to a lower energy configuration. This means the molecule transforms from a stable and unreactive state, to an unstable and highly reactive state. When light shines on an aromatic molecule, it can gain antiaromatic character because of a redistribution of its electrons. ![]() Compounds with antiaromatic character are unstable, reactive, and often have only fleeting existence. Compounds with aromatic character often are stable and unreactive. Wu, along with her research group, looked at the effects of aromaticity and antiaromaticity, a common molecular feature of cyclic organic compounds, on light-driven reactions. This process is called photoexcitation, and the gained energy is useful for driving a number of reactions. When light hits an electron, it gives the electron a jolt of energy. ![]() In a light-driven organic reaction, the first step is the excitement of an electron. Photoexcitation: Transfer of Light Energy to Electrons “We recognized that when light strikes an organic compound, there is a pattern that determines whether or not a proton transfer reaction will likely happen,” said Judy Wu, assistant professor of chemistry in the College of Natural Sciences and Mathematics and corresponding author for the paper. In a recent paper, published in the journal Proceedings of National Academy of Sciences, chemists at the University of Houston unfold fundamental principles that underlie light-driven proton transfer in organic molecules. These examples are just a fraction of the biologically important reactions which depend on light. In the human body, vitamin D can be made in the skin from exposure to sunlight. In photosynthesis, plants use sunlight to convert carbon dioxide and water into glucose and oxygen. In nature, a large number of organic and biological reactions are driven by light. Proton Transfer Forms Basis of Many Light-Driven Organic Reactions ![]()
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