1. Klein, Organic Chemistry 2e
8.9 The E1 Mechanism
The E1 mechanism is a 2-step process
Similar to SN1 (chapter 7), the reaction rate for E1 is not affected by the concentration of the base
What does the E and the 1 stand for in the E1 notation?
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

2. Klein, Organic Chemistry 2e
8.9 The E1 Mechanism
Given the rate law for E1, which step in the mechanism is the rate-determining slow step?
If the second step were the slow step, how would you write the rate law?
Practice with conceptual checkpoint 8.26
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

3. 8.9 The Effect of Substrate on E1
How does the substrate reactivity trend for E1 compare to the trend we discussed in chapter 7 for SN1? WHY?
Just like we did for SN1 in chapter 7, to explain the reactivity trend above, we must compare the energy diagrams for each substrate
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

4. 8.9 The Effect of Substrate on E1
To compare their energies, draw the structures for each transition state, intermediate, and product below
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

5. 8.9 The Effect of Substrate on E1
Because E1 and SN1 proceed by the same first step, their competition will generally result in a mixture of products
How might you promote one reaction
over the other?
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

6. 8.9 The Effect of Substrate on E1
Alcohols can also undergo elimination or dehydration by E1, but the –OH group is not a stable leaving group
In the E1 reaction below, once the water leaving group leaves the carbocation, what base should be used to complete the elimination?
Practice with conceptual checkpoint 8.27
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

7. 8.9 Regioselectivity for E1
The final step of the E1 mechanism determines the regioselectivity
E1 reactions generally produce the Zaitsev product predominantly. WHY?
Why can’t we control the regioselectivity in this reaction like we can in and E2 reaction?
Practice with SkillBuilder 8.8
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

8. 8.9 Stereoselectivity for E1
In the last step of the mechanism, a proton is removed from a β carbon adjacent to the sp2 hybridized carbocation
Draw the appropriate carbocation that forms in the reaction below, and rationalize the product distribution
Practice with conceptual checkpoint 8.31
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

9. 8.9 Stereoselectivity for E1
Considering stereochemistry and regiochemistry, predict the products if the molecule below was treated with concentrated sulfuric acid
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

10. Klein, Organic Chemistry 2e
8.10 Complete E1 Mechanisms
Recall the similarities between SN1 and E1
After the carbocation is formed and possibly rearranged, the E1 proton transfer neutralizes the charge
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

11. Klein, Organic Chemistry 2e
8.10 Complete E1 Mechanisms
Why is the first proton transfer necessary?
Practice with conceptual checkpoint 8.32
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

12. Klein, Organic Chemistry 2e
8.10 Complete E1 Mechanisms
Explain why the carbocation rearranges
Practice with conceptual checkpoint 8.33
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

13. Klein, Organic Chemistry 2e
8.10 Complete E1 Mechanisms
The maximum number of steps in an E1 mechanism is generally four
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

14. Klein, Organic Chemistry 2e
8.10 Complete E1 Mechanisms
Consider the energy diagram for the mechanism on the previous slide
Assess each free energy change
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e

15. Klein, Organic Chemistry 2e
8.10 Complete E1 Mechanisms
The mechanism shows the formation of the major products
Predict the minor elimination products as well
Practice with SkillBuilder 8.9
Copyright © 2015 John Wiley & Sons, Inc. All rights reserved.
Klein, Organic Chemistry 2e