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The secrets of the Norrish reaction: Why this photochemical reaction can change high-precision 3D printing?
In today's high-tech era, the application of 3D printing technology continues to expand, and one of the key reactions is the Norrish reaction. The reaction is named after the British chemist Ronald George Willeford Norrish and occurs primarily in the photochemical reaction of ketones and aldehydes. These reactions are not only of great significance in synthetic chemistry, but are also increasingly valued in environmental chemistry and materials science.
Norish reaction types
Norish reactions can be divided into two types: Type I and Type II.
Type I
The Norrish Type I reaction is the photochemical cleavage of ketones and aldehydes, also known as α-cleavage, to produce two free radical intermediates. This process involves photon absorption by the carbonyl group, which excites the carbonyl group to a photochemical singlet state and can obtain a triplet state through an intrasystem crossover, ultimately leading to the formation of an intermediate.
"These radicals can recombine into the original carbonyl compounds and undergo other secondary reactions."
The signal of Type I reaction is particularly important in the field of photopolymerization, especially in the development of photoinitiators. After being excited by ultraviolet light or visible light, the photoinitiator undergoes a photocleavage reaction, and the generated free radicals can effectively initiate monomer polymerization, achieving high-precision 3D structure design.
"This makes the Norrish Type I reaction a fundamental mechanism in high-resolution additive manufacturing processes."
Type II
Unlike Type I, the Norrish Type II reaction involves the photochemical reaction of a carbonyl compound to generate a 1,4-diradical via the abstraction of γ-hydrogen. This reaction can result in a decomposition reaction to produce an alkene and a ketone, or an internal recombination of the two radicals to form a substituted cyclobutane."These reactions demonstrate the potential of the Norrish reaction in organic synthesis, although its synthetic utility is not as broad as that of the Type I reaction."
Environmental impact and application
In addition to synthetic chemistry, the Norrish reaction also plays an important role in environmental chemistry. For example, the photolysis of seven-carbon aldehydes simulates chemical reactions in nature to produce alkynes and aldehyde compounds, which provide important experimental data for environmental science.
"A study found that gold nanoparticles can be generated using free radicals generated by photolysis in water with hydrogen tetrachloroauric acid, showing the synthetic potential of the reaction."
Actual Cases and Future Prospects
In 1982, Leo Paquette completed the synthesis of decacycloalkanes using three different Norrish reactions, demonstrating the potential value of this reaction in organic synthesis. In addition, Phil Baran et al. successfully maximized the use of the Norrish Type II reaction in the total synthesis of the active compound ouabagenin, demonstrating its effectiveness in practical synthesis.
"With advances in materials science and 3D printing technology, the Norrish reaction may become an important driving force in the development of new materials in the future."
Of course, the Norrish reaction is of great significance in organic synthesis and materials science, but what insights can these photochemical reactions bring us in improving the accuracy and efficiency of 3D printing?
