Textbook Question
Each of these compounds can react as a nucleophile. In each case, use curved arrows to show how the nucleophile would react with the strong electrophile BF3.
(e) CH3CH2OH
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Ch. 2 - Acids and Bases; Functional Groups
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 2, Problem 54a,b
The pKa of ascorbic acid (vitamin C, page 55) is 4.17, showing that it is slightly more acidic than acetic acid (CH3COOH, pKa 4.74).
a. Show the four different conjugate bases that would be formed by deprotonation of the four different OH groups in ascorbic acid.
b. Compare the stabilities of these four conjugate bases, and predict which OH group of ascorbic acid is the most acidic.
Verified step by step guidance1
Identify the four hydroxyl (OH) groups in the structure of ascorbic acid. These are the groups that can potentially lose a proton to form conjugate bases.
For each OH group, consider the deprotonation process: remove the hydrogen ion (H⁺) from the OH group, leaving behind an oxygen atom with a negative charge (O⁻). This forms the conjugate base.
Examine the stability of each conjugate base formed. Stability can be influenced by factors such as resonance, inductive effects, and the electronegativity of surrounding atoms. Resonance stabilization is particularly important in organic chemistry.
Compare the conjugate bases: The conjugate base that is most stabilized by resonance or other effects will correspond to the most acidic OH group. Look for conjugate bases where the negative charge can be delocalized over multiple atoms.
Predict the most acidic OH group: Based on the stability analysis, determine which OH group is most likely to lose a proton. The most acidic OH group will be the one whose conjugate base is most stable.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
pKa and Acidity
The pKa value is a measure of the acidity of a compound, indicating the tendency of a compound to donate a proton. A lower pKa value means a stronger acid, as it more readily donates protons. In this context, ascorbic acid with a pKa of 4.17 is more acidic than acetic acid, which has a pKa of 4.74, meaning ascorbic acid donates protons more easily.
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07:45
Identifying pKa values
Conjugate Base Stability
The stability of a conjugate base is crucial in determining the acidity of its corresponding acid. A more stable conjugate base results in a stronger acid. Stability can be influenced by factors such as resonance, inductive effects, and electronegativity. In ascorbic acid, the stability of the conjugate bases formed by deprotonation of different OH groups will help predict which OH group is the most acidic.
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04:31Stability of Conjugated Intermediates
Resonance and Electron Delocalization
Resonance involves the delocalization of electrons across adjacent atoms, which can stabilize a molecule or ion. In organic acids, resonance can stabilize the conjugate base by spreading the negative charge over multiple atoms. For ascorbic acid, analyzing the resonance structures of the conjugate bases formed by deprotonation of each OH group will help determine which base is most stable and, consequently, which OH group is most acidic.
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Related Practice
Textbook Question
The pKa of ascorbic acid (vitamin C, page 55) is 4.17, showing that it is slightly more acidic than acetic acid (CH3COOH, pKa 4.74).
c. Compare the most stable conjugate base of ascorbic acid with the conjugate base of acetic acid, and suggest why these two compounds have similar acidities, even though ascorbic acid lacks the carboxylic acid (COOH) group.
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Textbook Question
Each of these compounds can react as a nucleophile. In each case, use curved arrows to show how the nucleophile would react with the strong electrophile BF3.
(f) (CH3)2S
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Textbook Question
Many naturally occurring compounds contain more than one functional group. Identify the functional groups in the following compounds:
a. Penicillin G is a naturally occurring antibiotic.
b. Dopamine is the neurotransmitter that is deficient in Parkinson’s disease.
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Textbook Question
Each of these compounds can react as a nucleophile. In each case, use curved arrows to show how the nucleophile would react with the strong electrophile BF3.
(a)
(b)
Textbook Question
Many naturally occurring compounds contain more than one functional group. Identify the functional groups in the following compounds:
d. Thyroxine is the principal thyroid hormone.
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