Q: What is the rate law for an $$S_N2$$ reaction?

$$\text{rate} = k[\text{RX}][\text{Nu}^-]$$

Question 1

Which of the following statements best describes the difference between a substitution and an elimination reaction?

Accepted Answer

Substitution reactions result in the electron-withdrawing group being replaced by another atom or group, while elimination reactions result in the electron-withdrawing group and a hydrogen on an adjacent carbon being removed.

Question 2

Which of the following alkyl halides is most reactive in an $$S_N2$$ reaction?

Accepted Answer

R–I

Question 3

What is the rate law for an $$S_N2$$ reaction?

Accepted Answer

$$	ext{rate} = k[	ext{RX}][	ext{Nu}^-]$$

Question 4

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

Accepted Answer

Dimethyl sulfoxide (DMSO)

Question 5

A tertiary alkyl halide reacts with water. Which mechanism is most likely?

Accepted Answer

$$S_N1$$

Question 6

Which of the following is true about the stereochemistry of $$S_N2$$ reactions?

Accepted Answer

The product has the inverted configuration relative to the reactant.

Question 7

Which of the following bases would most likely favor an E2 elimination over substitution when reacting with a secondary alkyl halide?

Accepted Answer

Potassium tert-butoxide ($$KO^tBu)$$

Question 8

According to Zaitsev’s rule, which alkene is the major product in an E2 elimination?

Accepted Answer

The more substituted alkene

Question 9

Which of the following statements about E1 reactions is correct?

Accepted Answer

E1 reactions can form more than one product due to carbocation rearrangements.

Question 10

Which of the following is a key difference between $$S_N1$$ and $$S_N2$$ mechanisms?

Accepted Answer

$$S_N1$$ involves a carbocation intermediate, while $$S_N2$$ does not.

Question 11

Which of the following conditions will favor elimination over substitution in a reaction with a secondary alkyl halide?

Accepted Answer

High temperature

Question 12

Which of the following statements about the stereochemistry of E2 reactions is correct?

Accepted Answer

Anti elimination is the preferred configuration.

Question 13

A student mixes 2-bromobutane with sodium ethoxide in DMSO. What is the major product?

Accepted Answer

2-butene (Zaitsev product)

Question 14

Which of the following is most likely to undergo rearrangement during a $$S_N1 or E1 $$reaction?

Accepted Answer

A secondary carbocation adjacent to a tertiary carbon

Question 15

Which of the following nucleophiles will react fastest in an $$S_N2$$ reaction with methyl bromide?

Accepted Answer

$$CN^-$$

Question 16

Which of the following statements is true regarding the products of E1 and E2 reactions?

Accepted Answer

Both E1 and E2 can produce E and Z isomers, with the E isomer (largest groups on opposite sides) usually being the major product.

Question 17

Which of the following best explains why $$S_N2$$ reactions do not occur with tertiary alkyl halides?

Accepted Answer

Steric hindrance prevents the nucleophile from attacking the carbon.

Question 18

Which of the following is a characteristic of a polar aprotic solvent?

Accepted Answer

It does not contain a hydrogen bonded to oxygen or nitrogen.

Question 19

A patient is exposed to a compound that undergoes rapid E2 elimination in the body. Which property of the compound most likely contributes to this reaction?

Accepted Answer

It contains a primary alkyl halide and is exposed to a strong base.

Chapter 12: Substitution and Elimination Reactions – Mechanisms, Stereochemistry, and Comparisons

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