Question 1

Which of the following statements best describes how a catalyst affects the activation energy of a reaction, as shown in the reaction coordinate diagrams?

Accepted Answer

A catalyst decreases the activation energy ($$\Delta G$$^{\ddagger}$$) of a reaction, making it faster.

Question 2

In the context of acid catalysis, what is the primary effect of protonating a carbonyl group during a nucleophilic addition reaction?

Accepted Answer

It increases the electrophilicity of the carbonyl carbon, making it more susceptible to nucleophilic attack.

Question 3

Which of the following is a key difference between specific-acid catalysis and general-acid catalysis?

Accepted Answer

Specific-acid catalysis requires a strong acid, while general-acid catalysis can use a weaker acid.

Question 4

Which of the following best explains why metal-bound hydroxide ions are better nucleophiles than water in metal-ion catalysis?

Accepted Answer

The metal ion stabilizes the negative charge on the hydroxide, increasing its nucleophilicity.

Question 5

Which of the following is NOT a way that a catalyst can increase the rate of a reaction?

Accepted Answer

By converting a leaving group into a stronger base.

Question 6

In the context of enzyme catalysis, what is the main advantage of the induced-fit model over the lock-and-key model?

Accepted Answer

The induced-fit model explains how enzymes can change conformation to better stabilize the transition state.

Question 7

Which of the following statements about nucleophilic catalysis is correct?

Accepted Answer

A nucleophilic catalyst forms a covalent intermediate with the reactant, changing the reaction mechanism.

Question 8

Why does the formation of a five-membered ring generally occur faster than the formation of a six-membered ring in intramolecular reactions?

Accepted Answer

Five-membered rings require fewer carbon–carbon bond rotations to achieve a favorable conformation.

Question 9

Which of the following best describes the role of Asp-102 in the catalytic triad of chymotrypsin, as revealed by site-specific mutagenesis?

Accepted Answer

Asp-102 stabilizes the developing positive charge on the imidazole ring of His-57, facilitating catalysis.

Question 10

Which of the following statements about the specificity of serine proteases is correct?

Accepted Answer

The binding pocket at the active site of the enzyme determines which substrates are cleaved.

Question 11

Which of the following best explains why an acid anhydride hydrolyzes faster than an ester?

Accepted Answer

The leaving group in an acid anhydride is a better leaving group than in an ester.

Question 12

Which of the following is a correct statement about the effect of a catalyst on the thermodynamics of a reaction?

Accepted Answer

A catalyst lowers the activation energy ($$\Delta G$$^{\ddagger}$$) but does not affect $$\Delta G^\circ$$.

Question 13

Which of the following is a real-world application of metal-ion catalysis in biological systems?

Accepted Answer

Metal ions stabilize negative charges developing on oxygen atoms during decarboxylation reactions.

Question 14

Which of the following best describes the effect of putting a reacting group and a catalyst in the same molecule (intramolecular catalysis)?

Accepted Answer

It increases the rate of the reaction by increasing the effective molarity.

Question 15

Which of the following statements about enzyme active sites is correct?

Accepted Answer

The active site brings reacting groups together in the proper orientation for reaction.

Question 16

Which of the following best explains why imidazole is a better nucleophile than water in nucleophilic catalysis?

Accepted Answer

Imidazole has a lone pair on nitrogen that is more available for nucleophilic attack.

Question 17

Which of the following is true regarding the effect of increasing reactant concentration on the rate of a catalyzed reaction?

Accepted Answer

Increasing concentration increases the frequency of collisions, thus increasing the reaction rate.

Question 18

Which of the following peptide bonds would be cleaved by chymotrypsin?

Accepted Answer

A peptide bond on the C-side of phenylalanine.

Catalysis in Organic and Enzymatic Reactions: Mechanisms and Applications

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