Which Sₙ2 reaction would you expect to be faster? Explain your answer. vs.

Verified step by step guidance

1. Identify the substrates involved in each S_N2 reaction.
2. Consider the steric hindrance around the electrophilic carbon in each substrate.
3. Recall that S_N2 reactions are faster with less sterically hindered substrates.
4. Evaluate the leaving group ability in each reaction, as a better leaving group can increase the reaction rate.
5. Compare the nucleophiles involved, if given, as stronger nucleophiles can also increase the reaction rate.

Key Concepts

Sₙ2 Mechanism

The Sₙ2 (substitution nucleophilic bimolecular) mechanism involves a single concerted step where a nucleophile attacks an electrophile, leading to the simultaneous displacement of a leaving group. This reaction is characterized by a second-order kinetics, meaning the rate depends on the concentration of both the nucleophile and the substrate. Understanding this mechanism is crucial for predicting reaction rates and outcomes.

Nucleophilicity

Nucleophilicity refers to the strength of a nucleophile in donating an electron pair to an electrophile. Factors influencing nucleophilicity include charge, electronegativity, and solvent effects. A stronger nucleophile will typically lead to a faster Sₙ2 reaction, as it can more effectively attack the electrophile and displace the leaving group.

Steric Hindrance

Steric hindrance describes the crowding around a reactive site that can impede the approach of a nucleophile to the electrophile. In Sₙ2 reactions, substrates with less steric hindrance (such as primary alkyl halides) react faster than those with more steric hindrance (like tertiary alkyl halides). Recognizing the impact of steric factors is essential for predicting the speed of Sₙ2 reactions.