Q: Which of the following statements best describes the rate law for an $$S_N2$$ reaction between methyl bromide and hydroxide ion?

The rate is second order overall: $$\text{rate} = k[\text{CH}_3\text{Br}][\text{OH}^-].$$

Question 1

Which of the following statements best describes the rate law for an $$S_N2$$ reaction between methyl bromide and hydroxide ion?

Accepted Answer

The rate is second order overall: $$	ext{rate} = k[	ext{CH}_3	ext{Br}][	ext{OH}^-].$$

Question 2

In an $$S_N2$$ reaction, which molecular orbital interaction is primarily responsible for the nucleophile's attack on the substrate?

Accepted Answer

The nucleophile's HOMO interacts with the substrate's LUMO.

Question 3

Which of the following alkyl halides would react fastest in an $$S_N2$$ reaction with $$\ce{OH^-} as $$the nucleophile?

Accepted Answer

1-bromopropane

Question 4

What is the stereochemical outcome at the carbon center undergoing substitution in an $$S_N2$$ reaction?

Accepted Answer

Inversion of configuration (Walden inversion)

Question 5

Which of the following is the best explanation for why $$S_N2$$ reactions do not occur at sp$$^2-$$hybridized carbons?

Accepted Answer

The planar geometry of sp$$^2-$$hybridized carbons prevents backside attack.

Question 6

Which of the following factors would most likely increase the rate of an $$S_N2$$ reaction?

Accepted Answer

Using a polar aprotic solvent

Question 7

A chemist wants to synthesize an ether using an $$S_N2$$ reaction. Which combination of reactants would be most effective?

Accepted Answer

Methyl bromide and sodium ethoxide

Question 8

Which of the following is a common feature of the transition state in an $$S_N2$$ reaction?

Accepted Answer

The carbon is bonded to five groups in a trigonal bipyramidal arrangement.

Question 9

Which of the following is the best leaving group for an $$S_N2$$ reaction?

Accepted Answer

$$\ce{I^-}$$

Question 10

Consider the following reaction: $$\ce{CH_3Br + OH^- \rightarrow CH_3OH + Br^-}. $$Which of the following statements is true regarding the molecular orbitals involved?

Accepted Answer

The $$\ce{OH^-}$$ donates electrons from its HOMO to the LUMO of $$\ce{CH_3Br}.$$

Question 11

Which of the following best explains why resonance delocalization in a nucleophile decreases its reactivity in $$S_N2$$ reactions?

Accepted Answer

Resonance delocalizes the lone pair, making it less available for attack.

Question 12

A student attempts an $$S_N2$$ reaction using 2-bromo-2-methylpropane and sodium cyanide. What is the most likely outcome?

Accepted Answer

No reaction due to steric hindrance at the tertiary carbon.

Question 13

Which of the following best describes the effect of increasing the size (bulkiness) of the nucleophile in an $$S_N2$$ reaction?

Accepted Answer

The reaction rate decreases due to steric hindrance.

Question 14

Which of the following solvents would most likely increase the rate of an $$S_N2$$ reaction?

Accepted Answer

Acetone

Question 15

A chiral alkyl halide undergoes an $$S_N2$$ reaction with a strong nucleophile. What is the configuration of the product relative to the starting material?

Accepted Answer

It is inverted relative to the starting material.

Question 16

Which of the following best explains why $$\ce{F^-} is a $$poor leaving group in $$S_N2$$ reactions?

Accepted Answer

$$\ce{F^-} is $$too basic and forms a strong bond with carbon.

Question 17

Which of the following is a real-world application of $$S_N2$$ chemistry?

Accepted Answer

Synthesis of ethers via Williamson ether synthesis.

Question 18

A reaction is performed between $$\ce{CH_3CH_2Br}$$ and $$\ce{NaCN} in $$acetonitrile. What is the major product?

Accepted Answer

$$\ce{CH_3CH_2CN}$$

Question 19

Which of the following best describes the energy profile of an $$S_N2$$ reaction?

Accepted Answer

It has a single transition state with one energy maximum.

Question 20

Which of the following statements about the $$S_N2$$ mechanism is correct?

Accepted Answer

The nucleophile attacks from the opposite side of the leaving group (backside attack).

The S<sub>N</sub>2 Reaction: Mechanism, Factors, and Stereochemistry

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