Q: Which of the following is the correct rate law for an $$S_N2$$ reaction between 1-bromopropane and hydroxide ion?

$$\text{rate} = k[\text{1-bromopropane}][\text{OH}^-]$$

Question 1

Which of the following statements best explains why tertiary alkyl halides react faster than primary alkyl halides in an $$S_N1$$ reaction?

Accepted Answer

Tertiary alkyl halides form more stable carbocations due to hyperconjugation and inductive effects from alkyl groups.

Question 2

Which of the following is the correct rate law for an $$S_N2$$ reaction between 1-bromopropane and hydroxide ion?

Accepted Answer

$$	ext{rate} = k[	ext{1-bromopropane}][	ext{OH}^-]$$

Question 3

A student attempts to synthesize 2-chloro-2-methylpropane from 2-methyl-2-propanol using HCl. Which mechanism is most likely involved in this transformation?

Accepted Answer

$$S_N1$$ mechanism

Question 4

Which of the following factors increases the rate of an $$E2$$ elimination reaction?

Accepted Answer

Using a strong, bulky base such as $$\mathrm{tBuO^-}$$

Question 5

In the dehydration of 3,3-dimethyl-2-butanol with acid, the major product is 2,3-dimethyl-2-butene. What is the mechanistic reason for this outcome?

Accepted Answer

A carbocation rearrangement (methyl shift) occurs to form a more stable tertiary carbocation before elimination.

Question 6

Which of the following best describes the stereochemical outcome of an $$S_N2$$ reaction?

Accepted Answer

Inversion of configuration at the stereocenter

Question 7

A chemist treats 2-bromopropane with sodium ethoxide in ethanol. Which product is expected to predominate, and by which mechanism?

Accepted Answer

Propene via $$E2$$

Question 8

Which of the following statements about Zaitsev’s rule is correct?

Accepted Answer

The most substituted alkene is formed preferentially in elimination reactions.

Question 9

Which of the following is the best leaving group for nucleophilic substitution reactions?

Accepted Answer

$$\mathrm{Br^-}$$

Question 10

In the $$E2$$ elimination of 2-bromobutane, which geometric relationship between the leaving group and the hydrogen being abstracted is required for the reaction to proceed most efficiently?

Accepted Answer

Anti periplanar

Question 11

Which of the following solvents would most favor an $$S_N2$$ reaction mechanism?

Accepted Answer

Dimethyl sulfoxide (DMSO)

Question 12

A reaction of 1-bromo-3-methylbutane with sodium cyanide in DMSO gives which major product and by which mechanism?

Accepted Answer

3-methyl-1-butanenitrile via $$S_N2$$

Question 13

Which of the following statements about the $$S_N1$$ reaction mechanism is FALSE?

Accepted Answer

The nucleophile concentration affects the reaction rate.

Question 14

Which of the following best explains the deuterium isotope effect observed in $$E2$$ eliminations?

Accepted Answer

C–D bonds are stronger and harder to break than C–H bonds, slowing the reaction when deuterium is present.

Question 15

Which of the following alkyl halides will NOT undergo an $$S_N2$$ reaction under typical conditions?

Accepted Answer

2-bromo-2-methylpropane (tert-butyl bromide)

Question 16

A solution of 2-bromobutane in ethanol is heated. Which of the following is the major product and by which mechanism?

Accepted Answer

2-butene via $$E1$$

Question 17

Which of the following best describes the effect of a polar protic solvent on the rate of an $$S_N2$$ reaction?

Accepted Answer

It decreases the rate by hydrogen bonding to the nucleophile.

Question 18

Which of the following is the correct IUPAC name for the compound shown below?

$$\mathrm{BrCH_2CH_2CH(CH_3$)CH_2CH_3}$$

Accepted Answer

1-bromo-4-methylpentane

Question 19

Which of the following best explains why $$S_N2$$ reactions are faster with methyl and primary alkyl halides than with tertiary alkyl halides?

Accepted Answer

Methyl and primary alkyl halides have less steric hindrance, allowing easier backside attack.

Question 20

A chemist wants to synthesize 2-methyl-2-butene from 2-bromo-2-methylbutane. Which base should be used to maximize the yield of the less substituted (Hofmann) alkene?

Accepted Answer

Potassium tert-butoxide ($$\mathrm{KOtBu})$$

Reactions of Alkyl Halides: Nucleophilic Substitutions and Eliminations

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