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The mysterious role of reaction intermediates: How do they influence the progress of chemical reactions?
In the world of chemical reactions, reaction intermediates play mysterious yet critical roles. These tiny compounds appear during the reaction but often do not show up in the final reaction equation. They are like supporting characters on the stage. Although they are not in the spotlight, they are the key to the operation of the whole story. What are reaction intermediates? How do they affect the course of chemical reactions?
Definition of reaction intermediates
According to the definition of the International Union of Pure and Applied Chemistry (IUPAC), a reaction intermediate is a compound whose lifetime in a chemical reaction exceeds the molecular vibration. They are formed from the reactants and then react further to form the final product of the reaction. Since they appear during the reaction but not in the overall reaction formula, this makes their role a special kind of "invisible" presence.
The existence of reaction intermediates emphasizes the complexity and diversity of chemical reactions, and their roles in different reaction processes turn each chemical reaction into a story.
Types of intermediates
Various reaction intermediates exist in chemical reactions, including carbon cations, carbon anions, and free radicals. Among them, carbon cations are common in olefin addition and nucleophilic substitution reactions. These intermediates have high energy and unstable states, so they are not easy to exist independently.
Carbocation
A carbocation is a carbon atom with a positive charge, often formed in addition reactions of olefins. When an alkene reacts with a hydrogen halogen, the π bond of the alkene combines with the hydrogen atom to form a carbocation intermediate, and then the halogen combines with the carbocation. Thus, this process demonstrates the importance of reaction intermediates in the synthesis of new compounds.
Carbanion
Compared to carbocations, carbanions are carbon atoms with negative charges and usually participate in reactions as strong nucleophiles. This type of intermediate is relatively stable and can be used to extend the carbon chain in synthetic reactions.
Free radicals
Free radicals are extremely unstable and short-lived intermediates whose unpaired electrons make them very reactive in reactions. This type of intermediate often appears in chain reactions such as methyl chloride. Once initiated, these processes may continue to occur, producing a variety of products.
The chain reactions involved in the formation and reaction of free radicals are complex and challenging, demonstrating their substitution and adaptability in chemical reactions.
Application of reaction intermediates
In biological systems, reaction intermediates also play important roles. For example, bacteria use an enzyme called metallo-β-lactamase to combat commonly used antibiotics, demonstrating the potential of reaction intermediates for use in biochemistry.
Reaction intermediates in the chemical industry
In the chemical industry, a reaction intermediate usually refers to a stable reaction product that has important value in other chemical industries. Common examples include cumene, produced from the reaction of benzene and propylene, which is further used to produce acetone and phenol.
These reaction intermediates are not only key components of chemical reactions, but also affect the entire chemical manufacturing process, demonstrating their indispensable value in industrial production.
The existence of reaction intermediates shapes the progress of chemical reactions in a quiet but powerful way. Whether on the laboratory desktop or on the industrial production line, they all show the chemical reaction in their own unique way. Fascinating microscopic world. Could these tiny but important compounds lead to new understandings of chemical reactions?
