Question 1

Which of the following statements best explains why $$\mathrm{F^-} is a $$poor nucleophile in polar protic solvents?

Accepted Answer

Polar protic solvents strongly solvate $$\mathrm{F^-}$$ due to its small size and localized charge, preventing it from acting as a nucleophile.

Question 2

In a polar aprotic solvent, which of the following anions is expected to be the best nucleophile?

Accepted Answer

$$\mathrm{F^-}$$

Question 3

Which factor is most important in determining the rate of an $$\mathrm{S_N2}$$ reaction?

Accepted Answer

Steric hindrance around the electrophilic carbon

Question 4

Why do tertiary alkyl halides rarely undergo $$\mathrm{S_N2}$$ reactions?

Accepted Answer

They are too sterically hindered for the nucleophile to perform a backside attack.

Question 5

Which of the following is the best leaving group for a nucleophilic substitution reaction?

Accepted Answer

$$\mathrm{I^-}$$

Question 6

A chemist is attempting an $$\mathrm{S_N1}$$ reaction with a secondary alkyl bromide. Which of the following changes would most likely increase the rate of the reaction?

Accepted Answer

Switching to a polar protic solvent

Question 7

Which of the following best describes the relationship between nucleophilicity and basicity in polar aprotic solvents?

Accepted Answer

Nucleophilicity parallels basicity; stronger bases are stronger nucleophiles.

Question 8

Which of the following nucleophiles would be most hindered by steric effects in an $$\mathrm{S_N2}$$ reaction?

Accepted Answer

$$\mathrm{tBuO^-}$$

Question 9

Which of the following statements about $$\mathrm{S_N1}$$ and $$\mathrm{S_N2}$$ reactions is correct?

Accepted Answer

$$\mathrm{S_N2}$$ reactions are favored by primary alkyl halides and good nucleophiles.

Question 10

Which of the following best explains why $$\mathrm{I^-} is a $$better nucleophile than $$\mathrm{F^-} in $$polar protic solvents?

Accepted Answer

$$\mathrm{I^-} is $$more polarizable and less tightly solvated, allowing it to escape the solvent shell and attack the substrate.

Question 11

Which of the following is a poor nucleophile and would be least likely to participate in an $$\mathrm{S_N2}$$ reaction?

Accepted Answer

$$\mathrm{H_2O}$$

Question 12

A primary alkyl halide is reacted with sodium azide ($$\mathrm{$$NaN_3$$}) in $$DMSO. Which mechanism and product are most likely?

Accepted Answer

$$\mathrm{S_N2}$$; inversion of configuration with azide substitution

Question 13

Which of the following statements about leaving groups is correct?

Accepted Answer

A good leaving group is a stable anion or neutral molecule.

Question 14

Which of the following best explains why $$\mathrm{RO^-} is a $$better nucleophile than $$\mathrm{ROH}$$?

Accepted Answer

$$\mathrm{RO^-} is an $$anion and thus more reactive toward electrophiles.

Question 15

Which of the following factors does NOT increase nucleophilicity?

Accepted Answer

Increasing the solvation of the nucleophile in a polar protic solvent

Question 16

Which of the following statements about allylic halides is true?

Accepted Answer

Primary allylic halides can undergo both $$\mathrm{S_N1}$$ and $$\mathrm{S_N2}$$ reactions due to resonance stabilization.

Question 17

Which of the following best describes the effect of $$\beta-$$branching on $$\mathrm{S_N2}$$ reactions?

Accepted Answer

$$\beta-$$branching decreases the rate of $$\mathrm{S_N2}$$ reactions due to increased steric hindrance.

Question 18

A student attempts an $$\mathrm{S_N2}$$ reaction on a tertiary alkyl bromide with sodium azide in acetone. What is the most likely outcome?

Accepted Answer

No reaction occurs due to excessive steric hindrance.

Question 19

Which of the following is the correct order of carbocation stability relevant to $$\mathrm{S_N1}$$ reactions?

Accepted Answer

Methyl \u003c 1° \u003c 2° \u003c 3°

Question 20

Which of the following combinations would most favor an $$\mathrm{S_N2}$$ reaction?

Accepted Answer

Primary alkyl halide, polar aprotic solvent, good nucleophile

Nucleophilicity, Solvent Effects, and Substitution Mechanisms (SN1 & SN2)

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