Question 1

Which of the following statements best explains why the E2 elimination reaction is regioselective, often favoring the more substituted alkene as the major product?

Accepted Answer

The more substituted alkene has a more stable transition state due to hyperconjugation and alkyl group electron donation.

Question 2

Given the following rate law for an E2 reaction: $$rate = k[alkyl\ halide][base]$$, what would happen to the reaction rate if the concentration of the base is doubled while keeping the alkyl halide concentration constant?

Accepted Answer

The reaction rate would double.

Question 3

Which of the following alkyl halides would react fastest in an E2 elimination reaction, assuming the same strong base is used in each case?

Accepted Answer

A tertiary alkyl halide

Question 4

In the E2 elimination of 2-bromobutane with methoxide ion, the major product is 2-butene. Why is this the case?

Accepted Answer

2-Butene is more substituted and thus more stable due to hyperconjugation.

Question 5

Which of the following best describes the stereochemical requirement for an E2 elimination to occur in a cyclohexane ring system?

Accepted Answer

The hydrogen and leaving group must both be in axial positions.

Question 6

A bulky base such as tert-butoxide reacts with 2-bromo-2-methylbutane. Which alkene is favored as the major product and why?

Accepted Answer

The less substituted alkene is favored due to steric hindrance preventing removal of the more hindered hydrogen.

Question 7

Which of the following is a key difference between the E1 and E2 elimination mechanisms?

Accepted Answer

E1 involves a carbocation intermediate, while E2 is a concerted process.

Question 8

Which of the following best explains why anti elimination is preferred in E2 reactions?

Accepted Answer

It allows for optimal orbital overlap and minimizes electron repulsion.

Question 9

A student treats 2-chloropentane with sodium methoxide. Which of the following is the major product and why?

Accepted Answer

2-Pentene, because it is the more substituted and more stable alkene.

Question 10

Which of the following statements about the E1 elimination of 2-bromo-2-methylpropane is correct?

Accepted Answer

The reaction proceeds via a tertiary carbocation intermediate.

Question 11

Which of the following best describes the effect of conjugation on the stability of alkenes formed in elimination reactions?

Accepted Answer

Conjugated alkenes are more stable due to delocalization of electrons.

Question 12

Which of the following is the correct order of carbocation stability?

Accepted Answer

$$tertiary \u003e secondary \u003e primary \u003e methyl$$

Question 13

Which of the following is the correct rate law for an E1 elimination reaction?

Accepted Answer

$$rate = k[alkyl\ halide]$$

Question 14

In the E2 elimination of a cyclohexane derivative, why might no reaction occur even if a strong base is present?

Accepted Answer

The leaving group and the hydrogen to be eliminated are not both axial.

Question 15

Which of the following best explains why (E)-2-pentene is the major product over (Z)-2-pentene in an E2 elimination?

Accepted Answer

(E)-2-pentene is more stable due to less steric strain between large groups.

Question 16

A student performs an E2 elimination on a six-membered ring and observes no reaction. What is the most likely explanation?

Accepted Answer

The hydrogen and leaving group are not both in axial positions.

Question 17

Which of the following is a real-world application of E2 elimination reactions?

Accepted Answer

Synthesis of alkenes used in the production of plastics such as polyethylene.

Question 18

Which of the following best describes the effect of a bulky base on the product distribution in an E2 reaction?

Accepted Answer

A bulky base favors the formation of the less substituted (Hofmann) alkene.

Question 19

Which of the following statements is true regarding the stereochemistry of E2 eliminations?

Accepted Answer

E2 eliminations are stereospecific, favoring anti-periplanar geometry.

Elimination and Substitution Reactions of Alkyl Halides: Mechanisms, Regioselectivity, and Stereochemistry

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