Late Transition State

Definition

The late transition state is a concept in organic chemistry that describes the structure of the transition state in a chemical reaction, particularly in the context of the Hammond Postulate. It refers to a transition state that is more product-like, meaning it more closely resembles the structure of the reaction's products rather than the reactants.

5 Must Know Facts For Your Next Test

1. The late transition state is more product-like in structure, meaning it more closely resembles the products of the reaction rather than the reactants.
2. According to the Hammond Postulate, a late transition state will have a structure that is similar to the products of the reaction, as the energy difference between the transition state and products is small.
3. The late transition state is associated with reactions that are exothermic (release energy) and have a small activation energy barrier.
4. The position of the transition state along the reaction coordinate is influenced by the relative stabilities of the reactants and products, as well as the activation energy barrier.
5. The late transition state is often observed in reactions that involve the formation of new carbon-carbon bonds or the cleavage of carbon-carbon bonds.

Review Questions

• Explain how the late transition state relates to the Hammond Postulate.
  • The late transition state is closely connected to the Hammond Postulate, which states that if two transition states differ in energy by less than 2-4 kcal/mol, they will have similar structures. In the case of a late transition state, the transition state more closely resembles the products of the reaction, as the energy difference between the transition state and the products is small. This is because the reaction is exothermic and has a low activation energy barrier, allowing the transition state to be more product-like in its structure.
• Describe the characteristics of a reaction that is likely to have a late transition state.
  • Reactions that are likely to have a late transition state are typically exothermic (release energy) and have a small activation energy barrier. This means that the transition state is closer in energy to the products than the reactants, allowing it to have a structure that more closely resembles the products. Additionally, reactions that involve the formation of new carbon-carbon bonds or the cleavage of carbon-carbon bonds are often associated with late transition states, as these processes are key steps in the conversion of reactants to products.
• Analyze how the position of the transition state along the reaction coordinate influences the structure of the late transition state.
  • The position of the transition state along the reaction coordinate is a key factor in determining the structure of the late transition state. If the transition state is closer to the products on the reaction coordinate, it will have a more product-like structure, as described by the late transition state concept. This is because the energy difference between the transition state and the products is small, allowing the transition state to more closely resemble the final products of the reaction. The relative stabilities of the reactants and products, as well as the activation energy barrier, influence the position of the transition state and, consequently, the structure of the late transition state.

Related terms

Transition State:

The transition state is the highest-energy intermediate along the reaction coordinate, representing the point at which the reactants are converting into the products.

Hammond Postulate:

The Hammond Postulate states that if two transition states differ in energy by less than 2-4 kcal/mol, they will have similar structures.

Reaction Coordinate:

The reaction coordinate is a diagram that depicts the energy changes that occur during a chemical reaction, with the transition state representing the highest-energy point.