Activation Energy, Transition State & Reaction Intermediates Explained

In summary, the conversation discusses the concept of activation energy, transition state, and reaction intermediates. It is clarified that the activation energy is the difference between the ground state of the reactants and the transition state, but it is unclear what exactly the transition state represents on a diagram. It is also mentioned that the transition state is not a chemical species, but rather a fleeting moment. In terms of the activation energy, it is suggested that the enzyme binds complementary to the transition state, which may lower the activation energy through noncovalent interactions. However, it is also stated that the enzyme does not directly bind to the transition state, but rather it appears after the enzyme binds to the molecule.
  • #1
lha08
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Homework Statement


I'm a little confused as to the concept of activation energy, transition state, and reaction intermediates...For example, I know that the activation energy is the difference between the ground state of the reactants and the transition state but on a diagram, does the top hill represent the transition state or the reaction intermediates? The thing is that supposedly the transition state is not a chemical species, its just a fleeting moment, but is this particular state represented by the reaction intermediates or is this state just between the formation of the ES and EP complexes?


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The Attempt at a Solution

 
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  • #2
If there is a multistep reaction, intermediates are in the valleys between tops occupied by transition states.
 
  • #3
Borek said:
If there is a multistep reaction, intermediates are in the valleys between tops occupied by transition states.

I'm just wondering, in terms of the activation energy, if the enzyme binds complementary to the transition state, is the activation energy first lowered by the binding energy that is released when some weak noncovalent interactions are formed between the enzyme-substrate complex, and then the binding energy that is released when the ES noncovalently binds further lowers the activation energy?
 
  • #4
I can be wrong, but as far as I can tell enzyme doesn't bind to the transition state, transition state appears after enzyme binds to the molecule.
 
  • #5


Activation energy, transition state, and reaction intermediates are all important concepts in chemical reactions. Let's break them down one by one.

Activation energy refers to the minimum amount of energy that must be supplied for a chemical reaction to occur. This energy is needed to break the bonds in the reactant molecules and form new bonds in the product molecules. The activation energy is represented by the energy barrier on a reaction energy diagram.

The transition state is a high-energy intermediate state that forms during a chemical reaction. It is the point at which the bonds in the reactant molecules are breaking and the bonds in the product molecules are forming. The transition state is often referred to as the "peak" or "top of the hill" on a reaction energy diagram. It is a fleeting moment and does not exist as a stable chemical species.

Reaction intermediates, on the other hand, are stable molecules that are formed during a chemical reaction but are not the final product. These intermediates are often represented by the valleys or plateaus on a reaction energy diagram. They can be formed before or after the transition state and are important in determining the overall rate and mechanism of a reaction.

To answer your question, the top hill on a reaction energy diagram represents the transition state, while the valleys or plateaus represent the reaction intermediates. The transition state is not a chemical species, but rather a high-energy state that is formed during the reaction.

I hope this helps clarify the concepts of activation energy, transition state, and reaction intermediates for you. Keep in mind that these are just simplified explanations and there may be more complex factors at play in specific reactions. As a scientist, it is important to continue learning and exploring these concepts in order to fully understand and manipulate chemical reactions.
 

1. What is activation energy?

Activation energy is the minimum amount of energy required for a chemical reaction to occur. It is often described as the "energy barrier" that must be overcome for the reactant molecules to form products.

2. How does activation energy affect the rate of a reaction?

The higher the activation energy, the slower the rate of the reaction. This is because a higher amount of energy is needed for the reactants to overcome the energy barrier and form products.

3. What is a transition state?

A transition state is a high-energy, unstable state that occurs during a chemical reaction. It is a temporary state in which the reactants are in the process of forming products and is often represented as the highest point on an energy diagram.

4. What are reaction intermediates?

Reaction intermediates are the molecules or compounds that are formed during a chemical reaction but are not the final products. They are formed in one step of the reaction and then consumed in a later step.

5. How can we determine the activation energy of a reaction?

The activation energy of a reaction can be determined experimentally by measuring the reaction rate at different temperatures and using the Arrhenius equation. It can also be estimated by analyzing the energy diagram of the reaction and identifying the energy of the transition state.

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