In this reaction, the ____________ is the nucleophile.

There will be a ______________ formed, and ______________ will be the leaving group.

The enzymes role is ______________________.

Question

In this reaction, the ____________ is the nucleophile.

There will be a ______________ formed, and ______________ will be the leaving group.

The enzymes role is ______________________.

BlackTom AI · Accepted Answer

A nucleophilic acyl substitution proceeds by attack of an active-site nucleophile (an enzyme residue) on the carbonyl carbon, so the enzyme is the nucleophile.

1. Relevant knowledge points and concepts
- Nucleophilic acyl substitution: a nucleophile attacks a carbonyl carbon (electrophile), converting the sp2 carbonyl into an sp3 tetrahedral intermediate; collapse of that intermediate expels a leaving group.
- Good leaving groups (like Cl−) depart on collapse; enzymes often use a nucleophilic side chain (serine, cysteine) to form a transient covalent (acyl-enzyme) intermediate — covalent catalysis provides an alternative reaction pathway.
- “Hemi-acetal” is a specific type of tetrahedral adduct formed with alcohol nucleophiles on aldehydes/ketones; the general name for attack on an acyl center is a tetrahedral intermediate.

2. Step-by-step reasoning process
- The carbonyl carbon is the electrophile; the drawn curved arrow shows attack from the enzyme’s nucleophilic atom (active-site residue) onto that carbonyl.
- That attack converts the C=O (sp2) into an sp3 center, producing a tetrahedral intermediate (central carbon with four single bonds and an oxyanion).
- The tetrahedral intermediate then collapses, reforming C=O and expelling the chloride as Cl− (chloride is shown on the substrate and is a good leaving group).
- The result is an acyl–enzyme species (enzyme covalently linked to the acyl group) before eventual hydrolysis or transfer to product.

3. Intermediate steps shown (electron flow)
- Enzyme Nu: lone pair → carbonyl C (bond forms).
- C=O π electrons → O (becomes O− in tetrahedral intermediate).
- Collapse: O− reforms C=O → C–Cl bond breaks → Cl− leaves.

4. Why the correct answer is correct
- The enzyme acts as nucleophile (attacks carbonyl).
- The immediate intermediate for acyl substitution is a tetrahedral intermediate (not a hemi-acetal in this context).
- Chloride is the leaving group (good leaving group attached to acyl carbon).
- The enzyme’s role is to provide an alternative (covalent) route to product by forming the acyl-enzyme intermediate (covalent catalysis), effectively changing the pathway.

5. Why other options are incorrect
- Options naming C=O as the nucleophile are wrong because the carbonyl is electrophilic, not nucleophilic.
- Options that list S− as the leaving group are incorrect: the leaving group shown is Cl, not a sulfur anion.
- Options invoking “hemi-acetal” misname the general tetrahedral acyl intermediate in enzyme acylation.

6. Conclusion
The correct answer (enzyme, tetrahedral intermediate, Cl, provide an alternative route to product) matches the provided answer.

In this reaction, the is the nucleophile. There will be a formed, and will be the leaving group. The enzymes role is __________.单项选择题

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In this reaction, the ____________ is the nucleophile. There will be a ______________ formed, and ______________ will be the leaving group. The enzymes role is ______________________.单项选择题

类似问题

Consider the reaction of ethanoyl chloride with methanol shown below. What product(s) may you expect to be formed from the reaction?

Consider the nucleophilic addition of ammonia to benzoyl chloride shown below. Which of the following statements is true?

Consider the nucleophilic addition of ammonia to benzoyl chloride shown below. Which of the following statements is true?

Consider the nucleophilic substitution of ammonia to benzoyl chloride shown below. Which of the following statements is true?

Compound (I) reacts with methanol to produce intermediate (II) and chloride ions. Which one of the following mechanisms is correct?

Consider the reaction of ethanoyl chloride with methanol shown below. What product(s) may you expect to be formed from the reaction?

Consider the nucleophilic addition of ammonia to benzoyl chloride shown below. Which of the following statements is true?

更多留学生实用工具

希望你的学习变得更简单

In this reaction, the is the nucleophile. There will be a formed, and will be the leaving group. The enzymes role is __________.单项选择题