Quiz - Alkyl Halides - Elimination Reactions - 3 | Alkyl Halides - Elimination Reactions

Organic Chemistry 1 - Quiz - Alkyl Halides - Elimination Reactions - 3


Which of the following factors does not favor E2 over E1 in an elimination reaction of alkyl halides?

Unlike the SN2 reactions which are inhibited by steric hindrance, the rate of the E1 and E2 reactions increases as the number of alkyl groups on the carbon bearing the leaving group increases. Indeed, the resulting alkene will be more substituted and therefore more stable. The nature of the alkyl halide does not allow us to determine which elimination mechanism occurs.


When analyzing the outcome of alkyl halide reactions, what is the Zaitsev product?

The Zaitsev (or Saytzeff) rule states that the alkene formed in elimination reactions is the one with the more substituted double bond, which is typically the most stable product.


Which of the following statements about E2 reactions is false?

E2 reactions are characterized by the concerted elimination of the leaving group and the deprotonation by the base. No carbocation intermediate is formed, distinguishing it from E1 reactions.


In an E1 reaction, the rate-determining step involves:

In E1 reactions, the rate-determining step is the formation of the carbocation intermediate through the loss of the leaving group. The reaction proceeds independently of the base's concentration.


Considering a tertiary alkyl halide, why would it be more likely to undergo an E1 reaction rather than an E2 reaction?

Tertiary alkyl halides are more likely to undergo E1 reactions because they can form tertiary carbocations, which are stabilized by hyperconjugation, making the E1 pathway favorable.


Which type of solvent would you choose to favor an E2 reaction for a primary alkyl halide?

Polar aprotic solvents are favored for E2 reactions because they stabilize ions poorly, thus facilitating the strong base to abstract a proton and forming the alkene directly.


Which of the following best characterizes a reaction that proceeds via an SN1 mechanism?

SN1 reactions are unimolecular nucleophilic substitution reactions where the rate of reaction depends only on the concentration of the substrate due to the formation of a carbocation intermediate.


What result would indicate a preference for E2 over SN2 in an elimination reaction using a strong bulky base?

Using a strong bulky base favors E2 elimination over SN2 substitution due to steric hindrance, and the most substituted alkene (Zaitsev product) is typically the major product.


In a competition between SN2 and E2 mechanisms, which structural feature of the substrate would preferentially lead to an E2 outcome?

Sterical hindrance in the substrate would make the SN2 mechanism less favorable due to the backside attack difficulty, thereby allowing the deprotonation step characteristic of the E2 mechanism to predominate.


A summary of SN1 vs. SN2 vs. E1 vs. E2 reactions would emphasize the importance of what factor in determining the pathway?

The characteristics of the nucleophile/base (strength and concentration), solvent effects, and the substrate's structure together play critical roles in determining which reaction pathway will be favored.