Consider the pair of reactions. Draw the organic products, then predict the type of substitution mechanism and compare the expected rates. Reaction 1: H2O : Br: product 1 CI: Reaction 2: H2O product 2 CI: Draw product 2. Draw product 1. Identify the mechanism of each reaction. Compare the rates of each reaction. Reaction 2 occurs by an SNI mechanism. Reaction 2 occurs by an SN 2 mechanism. Reaction 1 occurs by an Sn2 mechanism. Reaction 1 occurs by an Snl mechanism. Reaction 2 is faster than reaction 1. Reaction 1 is faster than reaction 2. Both reactions occur at the same rate.
The correct answer and explanation is:
The correct answers are:
- Reaction 1 occurs by an SN1 mechanism.
- Reaction 2 occurs by an SN2 mechanism.
- Reaction 2 is faster than reaction 1.
Explanation:
1. Identifying the Mechanism
Substitution reactions can occur via two primary mechanisms: SN1 (unimolecular nucleophilic substitution) and SN2 (bimolecular nucleophilic substitution).
- SN1 Mechanism (Reaction 1):
- This mechanism proceeds in two steps:
- Carbocation Formation: The leaving group (Br⁻) leaves first, creating a carbocation intermediate.
- Nucleophilic Attack: The nucleophile (H₂O) then attacks the carbocation to form the final product.
- The rate-determining step is the formation of the carbocation, which depends only on the concentration of the substrate.
- SN1 reactions occur faster in tertiary or secondary alkyl halides due to carbocation stability.
- This mechanism proceeds in two steps:
- SN2 Mechanism (Reaction 2):
- This mechanism occurs in one concerted step, where the nucleophile (H₂O) attacks from the opposite side of the leaving group (Cl⁻), leading to inversion of configuration.
- The reaction rate depends on both the substrate and the nucleophile.
- SN2 reactions occur faster in methyl or primary alkyl halides, as steric hindrance slows down the nucleophilic attack.
2. Comparing the Reaction Rates
- Reaction 2 (SN2) is faster than Reaction 1 (SN1) because:
- SN2 reactions do not require carbocation formation and proceed in a single step.
- In SN1, the rate-limiting step is slow carbocation formation.
- If Reaction 1 involves a secondary or tertiary alkyl halide, the steric hindrance slows down the reaction.
Thus, Reaction 2 (SN2) is faster than Reaction 1 (SN1).
Now, I will generate the images of the reaction products.
Here is the scientific illustration showing the organic reaction products for both nucleophilic substitution reactions (SN1 and SN2). The image includes curved arrows to indicate electron movement, highlighting the different mechanisms involved in each reaction. Let me know if you need further explanations!
