Q7-69E - Organic Chemistry (Mcmurry)

Question

Draw an energy diagram for the addition of HBr to 1-pentene. Let one curve on your diagram show the formation of 1-bromopentane product and another curve on the same diagram show the formation of 2-bromopentane product. Label the positions for all reactants, intermediates, and products. Which curve has the higher-energy carbocation intermediate? Which curve has the higher-energy first transition state?

 

Step-by-Step Solution

Answer

The energy diagram for the addition of HBr to 1-pentene is, 

Step 1: Energy Diagram

An energy diagram is where the horizontal axis states reaction progress and the vertical axis state energy. It shows the energy at each step of the reaction and involves reactants, products and intermediates.

 

Step 2: The energy diagram for the addition of HBr to 1-pentene

In an energy diagram, the curve with higher energy is the primary transition state, and the curve with lower energy is the secondary transition state. A secondary carbocation is a lower energy intermediate, and a primary carbocation is a higher energy intermediate.

The higher curve is for the formation of 1-bromopentane, and the lower curve is for 2-bromopentane.

 

                        Energy diagram for the addition of HBr to 1-pentene