Question 1

Which of the following statements best describes the stereochemical outcome of an $$\mathrm{S_N2}$$ reaction at a chiral center?

Accepted Answer

The configuration is inverted at the chiral center.

Question 2

Which of the following alkyl halides would react fastest in an $$\mathrm{S_N1}$$ reaction?

Accepted Answer

tert-butyl bromide

Question 3

A student attempts to carry out an $$\mathrm{E2}$$ elimination on cyclohexyl bromide. Which of the following is required for the reaction to proceed efficiently?

Accepted Answer

The leaving group and the hydrogen to be eliminated must be in an anti-periplanar relationship.

Question 4

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

Accepted Answer

Tertiary alkyl halides are too sterically hindered for backside attack.

Question 5

Which of the following is a requirement for a molecule to undergo an $$\mathrm{E2}$$ elimination reaction?

Accepted Answer

A strong base and a good leaving group.

Question 6

During the dehydration of alcohols using concentrated acids, which mechanism is most commonly followed?

Accepted Answer

$$\mathrm{E1}$$

Question 7

Which of the following statements about $$\mathrm{S_N1}$$ and $$\mathrm{S_N2}$$ mechanisms is correct?

Accepted Answer

$$\mathrm{S_N1}$$ reactions can lead to racemization at a chiral center.

Question 8

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

Accepted Answer

$$\mathrm{I^-}$$

Question 9

In an $$\mathrm{E2}$$ reaction, which product is favored when a bulky base is used?

Accepted Answer

The less substituted alkene (Hofmann product)

Question 10

Which of the following best describes the geometry of a double bond in an alkene?

Accepted Answer

Trigonal planar

Question 11

A chemist is trying to synthesize an alkene from a secondary alkyl halide. Which combination of base and reaction conditions will most likely favor an $$\mathrm{E2}$$ mechanism over $$\mathrm{S_N2}$$?

Accepted Answer

A strong, bulky base in a polar aprotic solvent at high temperature

Question 12

Which of the following statements about the $$\mathrm{E1}$$ mechanism is correct?

Accepted Answer

A carbocation intermediate is formed.

Question 13

Which of the following is a necessary condition for a nucleophile to participate in an $$\mathrm{S_N2}$$ reaction?

Accepted Answer

The nucleophile must be strong and able to attack from the backside.

Question 14

Which of the following best explains why $$\mathrm{S_N1}$$ reactions are faster in polar protic solvents?

Accepted Answer

Polar protic solvents stabilize the carbocation intermediate.

Question 15

A student is asked to classify the following halide: $$\mathrm{CH_3CH_2CH_2Br}. $$Which type of alkyl halide is this?

Accepted Answer

Primary alkyl halide

Question 16

Which of the following is a key difference between $$\mathrm{S_N1}$$ and $$\mathrm{S_N2}$$ mechanisms?

Accepted Answer

$$\mathrm{S_N1}$$ reactions involve carbocation intermediates, while $$\mathrm{S_N2}$$ reactions do not.

Question 17

Which of the following is true regarding the dehydration of alcohols using concentrated acid?

Accepted Answer

The reaction forms a carbocation intermediate.

Question 18

Which of the following is a requirement for a good leaving group in nucleophilic substitution reactions?

Accepted Answer

It must be able to stabilize a negative charge.

Question 19

In the $$\mathrm{E2}$$ elimination of 2-bromobutane with sodium ethoxide, which alkene is the major product?

Accepted Answer

trans-2-butene

Question 20

Which of the following best describes the nucleophilicity trend for halide ions in polar aprotic solvents?

Accepted Answer

$$\mathrm{F^-} \u003e \mathrm{Cl^-} \u003e \mathrm{Br^-} \u003e \mathrm{I^-}$$

Alkyl Halides, Alkenes, and Nucleophilic Substitution/Elimination Mechanisms: Study Notes

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