Textbook Question
In each part, rank the compounds in order of increasing rate of nucleophilic attack at C=O by a strong nucleophile like methoxide.
(b)
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Ch. 21 - Carboxylic Acid Derivatives
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
Chapter 21, Problem 59a
In each part, rank the compounds in order of increasing rate of nucleophilic attack at C=O by a strong nucleophile like methoxide.
(a) 
Verified step by step guidance1
Step 1: Understand the concept of nucleophilic attack at the carbonyl group (C=O). The rate of nucleophilic attack depends on the electrophilicity of the carbonyl carbon, which is influenced by the electron-withdrawing or electron-donating effects of substituents attached to the carbonyl group.
Step 2: Identify the compounds provided in the problem. Examine the substituents attached to the carbonyl group in each compound. Substituents that withdraw electron density from the carbonyl carbon increase its electrophilicity, making it more susceptible to nucleophilic attack.
Step 3: Consider steric hindrance. Bulky substituents near the carbonyl group can slow down the rate of nucleophilic attack by physically blocking access to the carbonyl carbon.
Step 4: Rank the compounds based on the combined effects of electronic factors (electron-withdrawing or donating substituents) and steric factors. Compounds with strong electron-withdrawing groups and minimal steric hindrance will have the fastest rate of nucleophilic attack.
Step 5: Verify your ranking by comparing the substituents in each compound and their effects on the carbonyl carbon's electrophilicity and accessibility. Ensure the order reflects increasing rate of nucleophilic attack.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Nucleophilicity
Nucleophilicity refers to the ability of a nucleophile to donate an electron pair to an electrophile, such as a carbonyl carbon in a C=O bond. Strong nucleophiles, like methoxide (CH3O-), are more reactive due to their high electron density and ability to stabilize negative charge. Understanding the factors that influence nucleophilicity, such as charge, electronegativity, and solvent effects, is crucial for predicting reaction rates.
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Nucleophilic Addition
Electrophilicity of Carbonyl Compounds
Carbonyl compounds (C=O) are characterized by a polarized double bond, where the carbon atom is electrophilic due to the partial positive charge created by the electronegative oxygen. The electrophilicity of the carbonyl carbon can be influenced by substituents attached to it; electron-withdrawing groups increase electrophilicity, while electron-donating groups decrease it. This concept is essential for ranking the reactivity of different carbonyl compounds towards nucleophilic attack.
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Steric Hindrance
Steric hindrance refers to the repulsion between atoms that occurs when they are brought close together, which can impede the approach of a nucleophile to an electrophile. In the context of carbonyl compounds, bulky substituents around the carbonyl can hinder nucleophilic attack, leading to slower reaction rates. Evaluating the steric environment of the carbonyl carbon is important for determining the order of reactivity among different compounds.
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Related Practice
Textbook Question
Methyl p-nitrobenzoate has been found to undergo saponification faster than methyl benzoate.
(b) Would you expect methyl p-methoxybenzoate to undergo saponification faster or slower than methyl benzoate?
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Textbook Question
Methyl p-nitrobenzoate has been found to undergo saponification faster than methyl benzoate.
(a) Consider the mechanism of saponification, and explain the reasons for this rate enhancement.
Textbook Question
Show how you would accomplish the following multistep syntheses, using the indicated starting material and any necessary reagents.
(d)
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Textbook Question
In Section 21-16, we saw that Sevin insecticide is made by the reaction of 1-naphthol with methyl isocyanate. A Union Carbide plant in Bhopal, India, once used this process to make Sevin for use as an agricultural insecticide. On December 3,1984, either by accident or by sabotage, a valve was opened that admitted water to a large tank of methyl isocyanate. The pressure and temperature within the tank rose dramatically, and pressure-relief valves opened to keep the tank from bursting. A large quantity of methyl isocyanate rushed out through the pressure-relief valves, and the vapors flowed with the breeze into populated areas, killing about 2500 people and injuring many more.
(a) Write an equation for the reaction that took place in the tank. Explain why the pressure and temperature rose dramatically.
(b) Propose a mechanism for the reaction you wrote in part (a).
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Textbook Question
Explain this curious result. What does this reaction tell you about the relative reactivity of esters and ketones?
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