Textbook Question
Rank the following radicals in decreasing order of stability. Classify each as primary, secondary, or tertiary.
a. The isopentyl radical,
b. The 3-methyl-2-butyl radical,
c. The 2-methyl-2-butyl radical,
d.
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Ch.4 - The Study of Chemical Reactions
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 4, Problem 31
Acetylacetone (pentane-2,4-dione) reacts with sodium hydroxide to give water and the sodium salt of a carbanion. Write a complete structural formula for the carbanion, and use resonance forms to show the stabilization of the carbanion.
Verified step by step guidance1
Identify the acidic hydrogen in acetylacetone. The hydrogen atom on the carbon between the two carbonyl groups (CH2) is acidic due to the electron-withdrawing effect of the carbonyl groups.
When acetylacetone reacts with sodium hydroxide, the hydroxide ion (OH-) abstracts the acidic hydrogen, forming water and leaving behind a carbanion at the central carbon.
Draw the carbanion structure: The central carbon now has a negative charge, represented as CH2^- between the two carbonyl groups.
Illustrate resonance stabilization: The negative charge on the carbanion can be delocalized to the oxygen atoms of the carbonyl groups. Draw resonance structures showing the negative charge moving to each oxygen atom, forming enolate ions.
Explain the resonance: The resonance forms show that the negative charge is shared between the central carbon and the oxygen atoms, which stabilizes the carbanion through resonance delocalization.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Carbanions
Carbanions are negatively charged species that contain a carbon atom with three bonds and a lone pair of electrons. They are typically formed when a carbon atom gains an electron, resulting in a formal negative charge. Carbanions are important intermediates in organic reactions, often acting as nucleophiles due to their high electron density.
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Resonance Stabilization
Resonance stabilization occurs when a molecule can be represented by two or more valid Lewis structures, known as resonance forms. These forms contribute to the overall stability of the molecule, as the actual structure is a hybrid of these forms. In the case of carbanions, resonance can delocalize the negative charge over multiple atoms, reducing the energy and increasing stability.
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Acetylacetone Reactivity
Acetylacetone (pentane-2,4-dione) is a β-diketone that can easily form enolates in the presence of a base like sodium hydroxide. The deprotonation of one of the acidic hydrogen atoms adjacent to the carbonyl groups leads to the formation of a carbanion. This reaction is significant in organic synthesis, as it allows for the formation of various derivatives through nucleophilic substitution.
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Related Practice
Textbook Question
The following reaction is a common synthesis used in the organic chemistry laboratory course.
When we double the concentration of methoxide ion (CH3O–), we find that the reaction rate doubles. When we triple the concentration of 1-bromobutane, we find that the reaction rate triples.
a. What is the order of this reaction with respect to 1-bromobutane? What is the order with respect to methoxide ion? Write the rate equation for this reaction. What is the overall order?
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Textbook Question
Write an equation for the reaction of vitamin E with an oxidizing radical (RO•) to give ROH and a less reactive free radical.
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Textbook Question
The triphenylmethyl cation is so stable that some of its salts can be stored for months. Explain why this cation is so stable.
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Textbook Question
Acetonitrile (CH3C≡N) is deprotonated by very strong bases. Write resonance forms to show the stabilization of the carbanion that results.
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Textbook Question
When it is strongly heated, ethyl diazoacetate decomposes to give nitrogen gas and a carbene. Draw a Lewis structure of the carbene.
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