Q: Which of the following is the correct rate law for an $$S_N2$$ reaction?

$$\text{rate} = k[\text{nucleophile}][\text{substrate}]$$

Question 1

Which of the following statements best explains why tertiary alkyl halides do not undergo $$S_N2$$ reactions efficiently?

Accepted Answer

Tertiary alkyl halides are too sterically hindered, preventing the nucleophile from attacking the electrophilic carbon in a backside attack.

Question 2

Which of the following solvents would most likely increase the rate of an $$S_N2$$ reaction involving a negatively charged nucleophile?

Accepted Answer

Dimethyl sulfoxide (DMSO)

Question 3

A chemist wants to convert 1-butanol to 1-bromobutane. Which of the following best describes the first step to make the hydroxyl group a better leaving group?

Accepted Answer

Protonate the alcohol with a strong acid such as $$HBr.$$

Question 4

Which of the following is the correct rate law for an $$S_N2$$ reaction?

Accepted Answer

$$	ext{rate} = k[	ext{nucleophile}][	ext{substrate}]$$

Question 5

Which of the following best describes the stereochemical outcome of an $$S_N2$$ reaction at a chiral center?

Accepted Answer

The configuration is always inverted (backside attack).

Question 6

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

Accepted Answer

$$I^-$$

Question 7

A student attempts an $$S_N2$$ reaction using 2-bromopropane and sodium methoxide in methanol. Which factor will most limit the reaction rate?

Accepted Answer

The substrate is secondary and sterically hindered.

Question 8

Which of the following statements about $$S_N1$$ reactions is correct?

Accepted Answer

The reaction involves a carbocation intermediate and the rate depends only on the substrate.

Question 9

Which of the following alkyl halides would react fastest in an $$S_N1$$ reaction?

Accepted Answer

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

Question 10

What is the expected stereochemical outcome when a chiral alkyl halide undergoes an $$S_N1$$ reaction?

Accepted Answer

A racemic mixture of enantiomers.

Question 11

Which of the following best explains why polar protic solvents decrease the rate of $$S_N2$$ reactions with anionic nucleophiles?

Accepted Answer

They solvate and stabilize the anion, making it less available to attack the substrate.

Question 12

Which of the following is a common feature of both $$S_N1$$ and $$S_N2$$ reactions?

Accepted Answer

Both involve the substitution of a leaving group by a nucleophile.

Question 13

A chemist is performing a nucleophilic substitution on 2-chloro-2-methylpropane in water. Which mechanism is most likely and why?

Accepted Answer

$$S_N1$$, because the substrate is tertiary and water is a weak nucleophile.

Question 14

Which of the following best describes the effect of a better leaving group on the rate of $$S_N1$$ and $$S_N2$$ reactions?

Accepted Answer

It increases the rate of both $$S_N1$$ and $$S_N2$$ reactions.

Question 15

Which of the following nucleophiles would be most effective in an $$S_N2$$ reaction in DMSO?

Accepted Answer

$$CH_3O^-$$

Question 16

A student mixes 1-bromobutane with sodium ethoxide in ethanol. Which product is expected from an $$S_N2$$ reaction?

Accepted Answer

1-ethoxybutane

Question 17

Which of the following best explains why methyl halides react faster than primary or secondary halides in $$S_N2$$ reactions?

Accepted Answer

Methyl halides have the least steric hindrance, allowing easier backside attack.

Question 18

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

Accepted Answer

The reaction proceeds through a two-step mechanism involving a carbocation intermediate.

Question 19

Which of the following is the correct order of carbocation stability, from most to least stable, relevant to $$S_N1$$ reactions?

Accepted Answer

Tertiary \u003e secondary \u003e primary \u003e methyl

Alkyl Halides and Nucleophilic Substitution: SN2 and SN1 Mechanisms

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