Organic Chemistry : Help with E1 Reactions
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Example Questions
Example Question #1 : Elimination Mechanisms
The above image undergoes an E1 elimination reaction in a lab. The researchers note that the major product formed was the "Zaitsev" product. Which of the following compounds did the observers see most abundantly when the reaction was complete?
None of these
The Zaitsev product is the most stable alkene that can be formed. This is the major product formed in E1 elimination reactions, because the carbocation can undergo hydride shifts to stabilize the positive charge. The most stable alkene is the most substituted alkene, and thus the correct answer.
Example Question #1 : Elimination Mechanisms
Which series of carbocations is arranged from most stable to least stable?
Tertiary, secondary, primary, methyl
Methyl, primary, secondary, tertiary
Primary, secondary, tertiary, methyl
The stability of a carbocation depends only on the solvent of the solution
Methyl, tertiary, secondary, primary
Tertiary, secondary, primary, methyl
Tertiary carbocations are stabilized by the induction of nearby alkyl groups. Since the carbocation is electron deficient, it is stabilized by multiple alkyl groups (which are electron-donating). Less substituted carbocations lack stability.
Example Question #3 : Elimination Mechanisms
Which of the following is true for E2 reactions?
The proton and the leaving group should be anti-periplanar
The reaction is bimolecular
All of these
A double bond is formed
All of these
All are true for E2 reactions. E2 reactions are bimolecular, with the rate dependent upon the substrate and base. Both E1 and E2 reactions generally follow Zaitsev's rule and form the substituted double bond. The stereochemistry for E2 should be antiperiplanar (this is not necessary for E1).
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