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Kenichi Fukui's revolutionary discovery: Why is the interaction between HOMO and LUMO so important?
In the field of chemistry, Frontier Molecular Orbital Theory (FMO) is at the core of the study of chemical reaction mechanisms. The interaction between HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) not only helps us predict the direction of chemical reactions, but also provides insights into the interactions between molecules. Among them, Fukui Kenichi’s research provides us with a key perspective.
Historical exploration
The article published by Kenichi Fukui in 1952 proposed a molecular theory of reactivity to aromatic hydrocarbons, which is still widely valued today. Although Fukui's insights received some criticism at the time, he and Roald Hoffmann won the Nobel Prize in Chemistry for this work. Their research focuses on reaction mechanisms, particularly the influence of leading-edge molecular orbitals.
Kenichi Fukui's cutting-edge molecular orbital theory provides a simplified framework for understanding chemical reactions by analyzing the interactions between HOMO and LUMO.
Theoretical basis
Fukui realized that according to molecular orbital theory, a good approximation of reactivity could be found by examining HOMO and LUMO. His theory is based on three main observations: first, the occupied orbitals of two molecules repel each other; second, positive charges will attract opposite negative charges; third, occupied orbitals and unoccupied orbitals will interact, especially HOMO and Interactions between LUMOs.
Frontier molecular orbital theory not only provides a unified explanation of chemical reactions and selectivity, but is also consistent with the predictions of Woodward-Hoffmann.
Application examples
Cycladdition reaction
A cycloaddition reaction is a reaction in which at least two new bonds are formed simultaneously. These reactions usually involve the cyclic movement of molecular electrons and are consistent with the nature of a range transverse reaction. For example, the Diels–Alder reaction, the reaction between maleic anhydride and cyclopentadiene complies with the Woodward-Hoffmann rule. The reaction mechanism and stereoselectivity can be further analyzed through FMO theory, showing the advantages of end-group products.
σ-translocation reaction
The σ-translocation reaction involves the movement of σ bonds and the consequent change of π bonds. In a [1,5] translocation, if there is a color ring phase shift, the movement of the electrons will determine whether the reaction is allowed. During this process, the interactive relationship between HOMO and LUMO shows the feasibility of the reaction. FMO theory provides a key explanation here.
Electrocyclization reaction
The conversion of double bonds and single bonds is crucial in electrocyclization reactions. This reaction can be understood through the process of merging or separating σ bonds and π bonds. This process follows the Woodward-Hoffmann reaction rules, and the reaction mechanism can be deduced from the interaction between HOMO and LUMO.
Exploiting the interaction between HOMO and LUMO can provide in-depth understanding of chemical reaction pathways and predict their possible products.
Kenichi Fukui's cutting-edge molecular orbital theory is not only crucial to understanding the mechanism of chemical reactions, but also provides a new perspective to predict reactivity through HOMO and LUMO. With a deeper understanding of molecular interactions, how can scientists use this theory to further advance the study and application of chemical reactions?
