Question 1

Which of the following best explains why iodide (I−) is a better leaving group than chloride (Cl−) in nucleophilic substitution reactions?

Accepted Answer

Iodide is larger and can better stabilize the negative charge due to its size and polarizability.

Question 2

A student mixes sodium hydroxide (NaOH) with 2-bromopropane in aqueous solution. Which mechanism is most likely to occur, and what is the expected stereochemical outcome?

Accepted Answer

S_N2 mechanism with inversion of configuration.

Question 3

Which of the following statements correctly distinguishes between Brønsted-Lowry and Lewis acid-base theories?

Accepted Answer

Brønsted-Lowry bases are proton acceptors, while Lewis bases are electron pair donors.

Question 4

Which substrate would react fastest in an S_N1 reaction, assuming the same leaving group and nucleophile?

Accepted Answer

2-Bromo-2-methylpropane ((CH3)3CBr)

Question 5

Which of the following is NOT a good leaving group for nucleophilic substitution reactions?

Accepted Answer

Hydroxide (OH−)

Question 6

A chemist wants to synthesize an ether by reacting sodium ethoxide (NaOEt) with 1-bromobutane. Which mechanism is most likely, and why?

Accepted Answer

S_N2, because sodium ethoxide is a strong nucleophile and 1-bromobutane is primary.

Question 7

Which factor most strongly favors the S_N1 mechanism over the S_N2 mechanism?

Accepted Answer

A highly substituted (tertiary) carbon center

Question 8

In a reaction where a nucleophile attacks a carbon atom and a leaving group departs simultaneously, what is the expected stereochemical outcome and what is this mechanism called?

Accepted Answer

Inversion of configuration; S_N2

Question 9

Which of the following best describes the role of a nucleophile in a Lewis acid-base reaction?

Accepted Answer

It donates an electron pair to the Lewis acid.

Question 10

Rank the following leaving groups in order of increasing leaving group ability: F−, Cl−, Br−, I−.

Accepted Answer

F− \u003c Cl− \u003c Br− \u003c I−

Question 11

A reaction between water and tert-butyl bromide (2-bromo-2-methylpropane) produces tert-butyl alcohol. Which of the following statements is true about this reaction?

Accepted Answer

It proceeds via an S_N1 mechanism with racemization.

Question 12

Which of the following best explains why primary alkyl halides favor S_N2 mechanisms?

Accepted Answer

Primary alkyl halides are less sterically hindered, allowing nucleophiles to attack more easily.

Question 13

Which of the following is the correct rate law for an S_N1 reaction?

Accepted Answer

Rate = k[RX]

Question 14

A chemist is comparing the reactivity of three alkyl halides toward S_N2 substitution: methyl bromide, 1-bromopropane, and 2-bromopropane. Which is the correct order of reactivity (most to least reactive)?

Accepted Answer

Methyl bromide \u003e 1-bromopropane \u003e 2-bromopropane

Question 15

Which of the following is a common misconception about nucleophilic substitution reactions?

Accepted Answer

A strong nucleophile always leads to an S_N2 mechanism, regardless of substrate structure.

Question 16

In a pharmaceutical synthesis, a chemist needs to ensure that a chiral center in a drug molecule is inverted during a substitution reaction. Which conditions should be chosen?

Accepted Answer

Use a primary alkyl halide and a strong nucleophile.

Question 17

Which of the following best describes the electron flow in a Brønsted-Lowry acid-base reaction?

Accepted Answer

Electrons flow from the base (nucleophile) to the acid (electrophile).

Question 18

Which of the following carbocations is most stabilized by resonance?

Accepted Answer

Benzyl carbocation

Question 19

A reaction between potassium cyanide (KCN) and benzyl chloride (C6H5CH2Cl) in DMSO proceeds rapidly. Which mechanism is most likely, and why?

Accepted Answer

S_N2, because benzyl chloride is primary and KCN is a strong nucleophile.

Question 20

Which of the following statements about the effect of nucleophile strength on substitution mechanisms is correct?

Accepted Answer

Strong nucleophiles favor S_N2 reactions.

Nucleophilic Substitution and Acid-Base Reactions: Mechanisms and Properties

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