Questions: Select all that apply Secondary alkyl halides may react by SN1 or SN2 reaction mechanisms. Which of the following will favor an SN1 mechanism over an SN2 mechanism? (Select all that apply.) - use of polar protic solvents - use of methanol as both the nucleophile and solvent - use of acetone as the solvent - use of a strong nucleophile

Select all that apply Secondary alkyl halides may react by SN1 or SN2 reaction mechanisms. Which of the following will favor an SN1 mechanism over an SN2 mechanism? (Select all that apply.)
- use of polar protic solvents
- use of methanol as both the nucleophile and solvent
- use of acetone as the solvent
- use of a strong nucleophile

Transcript text: Select all that apply Secondary alkyl halides may react by $S_{N 1} 1$ or $S_{N} 2$ reaction mechanisms. Which of the following will favor an $S_{N 1} 1$ mechanism over an $S_{N} 2$ mechanism? (Select all that apply.) use of polar protic solvents use of methanol as both the nucleophile and solvent use of acetone as the solvent use of a strong nucleophile Need help? Review these concept resources. Read About the Concept

Solution

Solution Steps

Step 1: Understanding the Reaction Mechanisms

Secondary alkyl halides can undergo nucleophilic substitution reactions via two main mechanisms: $S_{N1}$ and $S_{N2}$. The $S_{N1}$ mechanism involves a two-step process with the formation of a carbocation intermediate, while the $S_{N2}$ mechanism is a one-step process where the nucleophile attacks the substrate directly.

Step 2: Factors Favoring $S_{N1}$ Mechanism

The $S_{N1}$ mechanism is favored by conditions that stabilize the carbocation intermediate. These include:

Polar protic solvents: These solvents stabilize the carbocation and the leaving group through solvation.
Weak nucleophiles: Since the rate-determining step is the formation of the carbocation, the strength of the nucleophile is less important.
Solvents that can act as nucleophiles: Solvents like methanol can participate in the reaction, favoring $S_{N1}$.

Step 3: Evaluating the Options

Use of polar protic solvents: This favors the $S_{N1}$ mechanism as it stabilizes the carbocation.
Use of methanol as both the nucleophile and solvent: Methanol is a polar protic solvent and a weak nucleophile, favoring $S_{N1}$.
Use of acetone as the solvent: Acetone is a polar aprotic solvent, which typically favors $S_{N2}$ reactions.
Use of a strong nucleophile: Strong nucleophiles favor $S_{N2}$ reactions because they can directly attack the substrate.