Q: Which of the following is the correct rate law for an SN2 reaction between methyl chloride and hydroxide ion?

$$\text{Rate} = k[\text{CH}_3\text{Cl}][\text{OH}^-]$$

Q: Which of the following is the correct rate law for an SN1 reaction?

$$\text{Rate} = k[\text{substrate}]$$

Question 1

Which of the following statements best describes the difference between SN1 and SN2 mechanisms in nucleophilic substitution reactions?

Accepted Answer

SN2 reactions involve a concerted, single-step mechanism with inversion of configuration, while SN1 reactions proceed via a two-step mechanism involving a carbocation intermediate.

Question 2

Which of the following is the correct rate law for an SN2 reaction between methyl chloride and hydroxide ion?

Accepted Answer

$$	ext{Rate} = k[	ext{CH}_3	ext{Cl}][	ext{OH}^-]$$

Question 3

A student is attempting to carry out a nucleophilic substitution on tert-butyl bromide using a weak nucleophile in a polar protic solvent. Which mechanism is most likely to occur?

Accepted Answer

SN1, because the substrate is tertiary and the solvent is polar protic.

Question 4

Which of the following best explains why the SN2 reaction is fastest for methyl halides and slowest for tertiary alkyl halides?

Accepted Answer

Methyl halides have less steric hindrance, allowing easier backside attack by the nucleophile.

Question 5

During an SN2 reaction, what happens to the configuration of a chiral carbon center?

Accepted Answer

It is inverted.

Question 6

Which of the following is the correct rate law for an SN1 reaction?

Accepted Answer

$$	ext{Rate} = k[	ext{substrate}]$$

Question 7

A reaction produces a racemic mixture of enantiomers as the product. Which mechanism is most likely responsible?

Accepted Answer

SN1

Question 8

Which of the following best describes the transition state of an SN2 reaction?

Accepted Answer

The nucleophile and leaving group are both partially bonded to the central carbon.

Question 9

Which of the following statements about the energy profile of an SN1 reaction is correct?

Accepted Answer

The formation of the carbocation is the rate-determining step and corresponds to the highest energy barrier.

Question 10

Which of the following is NOT a requirement for a successful nucleophilic substitution reaction?

Accepted Answer

The leaving group must be a strong base.

Question 11

In the SN1 mechanism, why can the nucleophile attack from either side of the carbocation?

Accepted Answer

Because the carbocation is sp2 hybridized and planar.

Question 12

Which of the following real-life scenarios best illustrates the importance of leaving group ability in nucleophilic substitution reactions?

Accepted Answer

The use of alkyl halides in the synthesis of pharmaceuticals, where a good leaving group ensures efficient drug formation.

Question 13

Which of the following best explains why polar protic solvents favor SN1 reactions?

Accepted Answer

They stabilize the carbocation intermediate and the leaving group.

Question 14

A chemist wants to synthesize (R)-2-cyanobutane from (S)-2-bromobutane. Which mechanism should be used to ensure inversion of configuration?

Accepted Answer

SN2

Question 15

Which of the following is the correct order of reactivity for alkyl halides in SN2 reactions?

Accepted Answer

Methyl \u003e Primary \u003e Secondary \u003e Tertiary

Question 16

Which orbital interaction is crucial for the SN2 mechanism?

Accepted Answer

The HOMO of the nucleophile interacts with the LUMO (antibonding $$\sigma^*) of $$the electrophilic carbon.

Question 17

Which of the following best describes the energy of activation in a chemical reaction?

Accepted Answer

The minimum amount of extra energy required by a reacting molecule to get converted into product.

Question 18

Why are tertiary alkyl halides essentially inert to SN2 reactions?

Accepted Answer

Because of steric hindrance at the back side of the $$\alpha-$$carbon.

Question 19

Which of the following is a key feature of the SN2 reaction mechanism?

Accepted Answer

It involves simultaneous bond formation and bond breaking in a single transition state.

Question 20

In the context of nucleophilic substitution, what is a substrate?

Accepted Answer

A species at which the nucleophilic substitution reaction takes place.

Nucleophilic Substitution Reactions: SN1 and SN2 Mechanisms

Study Guide - Practice Questions

Study Guide - Flashcards