Q: Which of the following statements about the rate law for an $$\mathrm{S_N2}$$ reaction is correct?

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

Question 1

Which of the following statements best describes the difference between the mechanisms of $$\mathrm{S_N1}$$ and $$\mathrm{S_N2}$$ reactions?

Accepted Answer

$$\mathrm{S_N2}$$ reactions occur in a single step with simultaneous bond breaking and bond formation, while $$\mathrm{S_N1}$$ reactions occur in two steps with a carbocation intermediate.

Question 2

Which of the following alkyl halides is most likely to undergo an $$\mathrm{S_N1}$$ reaction?

Accepted Answer

Tertiary alkyl bromide ($$\mathrm{(CH_3$)_3CBr})$$

Question 3

In the $$\mathrm{S_N2}$$ reaction of $$\mathrm{CH_3CH_2Cl}$$ with $$\mathrm{OH^-} in$$ $$\mathrm{DMSO}$$, what is the expected stereochemical outcome at the reacting carbon?

Accepted Answer

Inversion of configuration

Question 4

Which of the following solvents would most likely favor an $$\mathrm{S_N1}$$ reaction over an $$\mathrm{S_N2}$$ reaction?

Accepted Answer

Methanol ($$\mathrm{CH_3OH})$$

Question 5

A reaction of $$\mathrm{2-$$bromo-2$$-methylpropane}$$ with water produces a mixture of substitution and elimination products. Which mechanism(s) is/are most likely involved?

Accepted Answer

Both $$\mathrm{S_N1}$$ and $$\mathrm{E1}$$

Question 6

Which of the following statements about the rate law for an $$\mathrm{S_N2}$$ reaction is correct?

Accepted Answer

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

Question 7

Which of the following nucleophiles would be most reactive in a polar aprotic solvent for an $$\mathrm{S_N2}$$ reaction?

Accepted Answer

$$\mathrm{F^-}$$

Question 8

In a $$\beta-$$elimination ($$\mathrm{E2}) $$reaction, which of the following is required for the reaction to proceed efficiently?

Accepted Answer

A strong base and an anti-periplanar arrangement of the leaving group and $$\beta-$$hydrogen

Question 9

Which of the following best explains why tertiary alkyl halides do not undergo $$\mathrm{S_N2}$$ reactions?

Accepted Answer

Steric hindrance prevents backside attack by the nucleophile.

Question 10

Which of the following statements about the stereochemistry of $$\mathrm{S_N1}$$ reactions is correct?

Accepted Answer

$$\mathrm{S_N1}$$ reactions result in racemization at the reacting center.

Question 11

Which of the following is the major product when 2-bromobutane reacts with $$\mathrm{NaOEt} in $$ethanol?

Accepted Answer

2-butene

Question 12

Which of the following factors increases the rate of $$\mathrm{S_N1}$$ reactions?

Accepted Answer

Increasing the stability of the carbocation intermediate

Question 13

Which of the following statements about the effect of solvent on $$\mathrm{S_N2}$$ reactions is correct?

Accepted Answer

Polar aprotic solvents increase the rate of $$\mathrm{S_N2}$$ reactions.

Question 14

Which of the following is a common leaving group in nucleophilic substitution reactions?

Accepted Answer

$$\mathrm{Br^-}$$

Question 15

Which of the following best describes the role of the nucleophile in a nucleophilic substitution reaction?

Accepted Answer

It donates a pair of electrons to form a new covalent bond with the substrate.

Question 16

In an $$\mathrm{E1}$$ elimination reaction, which step is rate-determining?

Accepted Answer

Formation of the carbocation intermediate

Question 17

Which of the following statements about $$\mathrm{E2}$$ reactions is correct?

Accepted Answer

$$\mathrm{E2}$$ reactions are favored by strong bases and anti-periplanar geometry.

Question 18

Which of the following is the major product when 1-bromo-2-methylcyclohexane reacts with $$\mathrm{NaOEt} in $$ethanol?

Accepted Answer

2-methylcyclohexene

Question 19

Which of the following best explains why benzylic and allylic halides undergo $$\mathrm{S_N1}$$ reactions more readily than methyl or primary alkyl halides?

Accepted Answer

Their carbocation intermediates are stabilized by resonance.

Nucleophilic Substitution and β-Elimination: Mechanisms, Factors, and Applications

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