Textbook Question
What are the products of the following reactions?
a.
b.
c.
d.
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Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
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Bruice 8th EditionCh. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid DerivativesProblem 28
Bruice 8th EditionCh. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid DerivativesProblem 28Chapter 17, Problem 28
Why is the pKa value of protonated hydroxylamine (6.0) so much lower than the value of a protonated primary amine such as protonated methylamine (10.7)?
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Understand the concept of pKa: The pKa value indicates the strength of an acid. A lower pKa value corresponds to a stronger acid, meaning the compound is more likely to donate a proton.
Examine the structure of protonated hydroxylamine: Protonated hydroxylamine has an -OH group attached to the nitrogen atom. The electronegativity of oxygen increases the electron-withdrawing effect, stabilizing the conjugate base after deprotonation and making the protonated form more acidic (lower pKa).
Compare with protonated methylamine: Protonated methylamine has a methyl group (-CH3) attached to the nitrogen atom. The methyl group is electron-donating, which destabilizes the conjugate base after deprotonation, making the protonated form less acidic (higher pKa).
Consider resonance and inductive effects: In protonated hydroxylamine, the lone pairs on the oxygen atom can interact with the nitrogen atom, further stabilizing the conjugate base. This effect is absent in protonated methylamine, contributing to the difference in pKa values.
Summarize the reasoning: The lower pKa value of protonated hydroxylamine compared to protonated methylamine is due to the electron-withdrawing effect of the -OH group and the stabilization of the conjugate base through resonance and inductive effects, making protonated hydroxylamine a stronger acid.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Protonation and pKa Values
Protonation refers to the addition of a proton (H+) to a molecule, which can significantly affect its acidity and basicity. The pKa value is a quantitative measure of the strength of an acid in solution; lower pKa values indicate stronger acids. In this context, the pKa values of protonated hydroxylamine and protonated methylamine reflect their relative stabilities and tendencies to donate protons.
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Resonance Stabilization
Resonance stabilization occurs when a molecule can be represented by multiple valid Lewis structures, allowing for the delocalization of electrons. In the case of protonated hydroxylamine, the positive charge can be delocalized over the nitrogen and oxygen atoms, which can lead to a less stable structure compared to protonated methylamine, where the positive charge is localized on the nitrogen atom.
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Inductive Effects
Inductive effects refer to the electron-withdrawing or electron-donating effects of substituents on a molecule, which can influence its acidity or basicity. In protonated methylamine, the alkyl group can donate electron density to the nitrogen, stabilizing the positive charge. In contrast, the presence of the electronegative oxygen in protonated hydroxylamine can withdraw electron density, making it less stable and resulting in a lower pKa.
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01:47Understanding the Inductive Effect.
Related Practice
Textbook Question
What are the products of the following reactions? (A trace amount of acid is present in each case.)
a. cyclopentanone + ethylamine
b. cyclopentanone + diethylamine
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Textbook Question
Imines can exist as stereoisomers. The isomers are named using the E,Z system of nomenclature (Section 4.2 ). The lone pair has the lowest priority.
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Draw the structure of each of the following compounds:
a. the (E)-hydrazone of benzaldehyde
b. the (Z)-oxime of propiophenone
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Textbook Question
A ketone can be prepared from the reaction of a nitrile with a Grignard reagent. Describe the intermediate formed in this reaction, and show how it can be converted to a ketone.
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Textbook Question
How would you make the following compounds from N-benzylbenzamide?
c. benzyl alcohol
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Textbook Question
The pKa of protonated acetone is about –7.5 and the pKa of protonated hydroxylamine is 6.0.
a. In a reaction with hydroxylamine at pH 4.5 (Figure 16.2), what fraction of acetone is present in its acidic, protonated form?
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