Domanda del libro di testo
Explain why bimolecular condensation is a poor method for making unsymmetrical ethers such as ethyl methyl ether.
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Ch. 14 - Ethers, Epoxides, and Thioethers
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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TOC.tableOfContents
- 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
Capitolo 14, Problema 12
Propose a mechanism for the acid-catalyzed condensation of n-propyl alcohol to n-propyl ether, as shown above. When the temperature is allowed to rise too high, propene is formed. Propose a mechanism for the formation of propene, and explain why it is favored at higher temperatures.
Guida verificata passo dopo passo1
Step 1: Begin by understanding the acid-catalyzed condensation mechanism for the formation of n-propyl ether from n-propyl alcohol. The process typically involves protonation of the alcohol to form a good leaving group.
Step 2: Protonation of n-propyl alcohol occurs when the alcohol oxygen atom donates a pair of electrons to a hydrogen ion (H⁺) from the acid catalyst, forming an oxonium ion. This is represented as:
Step 3: The oxonium ion can then undergo nucleophilic attack by another molecule of n-propyl alcohol, leading to the formation of n-propyl ether. This step involves the displacement of water as a leaving group, forming the ether linkage.
Step 4: For the formation of propene at higher temperatures, consider the elimination mechanism. The oxonium ion can lose a water molecule, forming a carbocation intermediate. This is followed by a deprotonation step, where a hydrogen ion is removed from the adjacent carbon, resulting in the formation of propene. This is represented as:
Step 5: Explain why propene formation is favored at higher temperatures. The elimination reaction leading to propene is an endothermic process, which means it requires heat to proceed. At higher temperatures, the energy barrier for elimination is overcome more easily, favoring the formation of propene over the condensation reaction.
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Acid-Catalyzed Condensation
Acid-catalyzed condensation is a reaction where an acid facilitates the formation of an ether from alcohols by promoting the nucleophilic attack of an alcohol on another alcohol molecule. The acid protonates the hydroxyl group, making it a better leaving group, which allows for the formation of a new C-O bond and the release of water. This process is crucial for understanding how n-propyl alcohol can be converted into n-propyl ether.
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03:09
Acid Catalyzed
Elimination Reaction
An elimination reaction involves the removal of a small molecule from a larger one, resulting in the formation of a double bond. In the context of n-propyl alcohol, when the temperature increases, the reaction can shift towards elimination, leading to the formation of propene. This occurs because higher temperatures favor the formation of products with greater entropy, such as alkenes, over the more stable ether.
Video consigliato:
00:40Recognizing Elimination Reactions.
Le Chatelier's Principle
Le Chatelier's Principle states that if a system at equilibrium is disturbed, the system will adjust to counteract the disturbance and restore a new equilibrium. In the case of the acid-catalyzed condensation and subsequent elimination reactions, increasing the temperature shifts the equilibrium towards the formation of propene, as the system seeks to minimize the effect of the added heat by favoring the endothermic elimination process.
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04:12The Electron Configuration
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Which of the following ethers can be formed in good yield by condensation of the corresponding alcohols? For those that cannot be formed by condensation, suggest an alternative method that will work.
(a) dibutyl ether
(b) ethyl n-propyl ether
(c) di-sec-butyl ether
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Show how the following ethers might be synthesized using (1) alkoxymercuration–demercuration and (2) the Williamson synthesis. (When one of these methods cannot be used for the given ether, point out why it will not work.)
f. tert-butyl phenyl ether
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Show how the following ethers might be synthesized using (1) alkoxymercuration– demercuration and (2) the Williamson synthesis. (When one of these methods cannot be used for the given ether, point out why it will not work.)
(e) 1-isopropoxy-1-methylcyclopentane
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Propose a mechanism for the following reaction.
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Predict the products of the following reactions. An excess of acid is available in each case.
(a) ethoxycyclohexane + HBr
(b) tetrahydropyran + HI
(c) anisole (methoxybenzene) + HBr
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