Domanda del libro di testo
Show how you would accomplish the following syntheses.
c. hexan-1-ol → 2-hydroxyheptanoic acid
918
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Ch. 18 - Ketones and Aldehydes
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 18, Problema 15
Propose a mechanism for each cyanohydrin synthesis just shown.
Guida verificata passo dopo passo1
Step 1: Identify the starting material and the reagent. In each case, the starting material is either an aldehyde or a ketone, and the reagent is hydrogen cyanide (HCN). The reaction is catalyzed by cyanide ions (CN⁻).
Step 2: Understand the mechanism. The cyanohydrin synthesis involves nucleophilic addition of the cyanide ion (CN⁻) to the carbonyl group (C=O) of the aldehyde or ketone. This is followed by protonation of the resulting alkoxide intermediate.
Step 3: Initiate the reaction. The cyanide ion (CN⁻) attacks the electrophilic carbon atom of the carbonyl group, breaking the π bond and forming a tetrahedral intermediate. Represent this step as:
Step 4: Protonation of the intermediate. The negatively charged oxygen atom in the tetrahedral intermediate is protonated by HCN, forming the cyanohydrin product. Represent this step as:
Step 5: Analyze the steric and electronic effects. The yield of cyanohydrin depends on the steric hindrance around the carbonyl group. For propanal, the reaction proceeds efficiently due to minimal steric hindrance. For butan-2-one, the yield is slightly lower due to increased steric hindrance. For di-tert-butylketone, the reaction is slow and yields are poor due to significant steric hindrance around the carbonyl group.
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Cyanohydrin Formation
Cyanohydrins are formed through the nucleophilic addition of hydrogen cyanide (HCN) to carbonyl compounds, such as aldehydes or ketones. In this reaction, the nucleophile (cyanide ion) attacks the electrophilic carbon of the carbonyl group, leading to the formation of a hydroxyl group and a cyano group on the same carbon atom.
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02:36
Nitrile Reduction
Nucleophilic Addition Mechanism
The nucleophilic addition mechanism involves the attack of a nucleophile on an electrophile, resulting in the formation of a new bond. In the case of cyanohydrin synthesis, the cyanide ion acts as the nucleophile, while the carbonyl carbon serves as the electrophile. This mechanism typically includes a tetrahedral intermediate before the final product is formed.
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08:27Nucleophilic Addition
Stereochemistry of Cyanohydrins
Cyanohydrins can exhibit stereochemistry due to the presence of a chiral center formed during their synthesis. The addition of HCN to the carbonyl carbon can lead to the formation of two enantiomers, depending on the orientation of the nucleophile's attack. Understanding the stereochemical implications is crucial for predicting the properties and reactivity of the resulting cyanohydrins.
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Percorso guidato
1:38Polymer Stereochemistry Concept 1
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Domanda del libro di testo
Sodium triacetoxyborohydride, NaBH(OAc)3, is a mild reducing agent that reduces aldehydes much more quickly than ketones. It can be used to reduce aldehydes in the presence of ketones, such as in the following reaction:
(b) Propose a mechanism for the reduction of an aldehyde by sodium triacetoxyborohydride.
3336
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Domanda del libro di testo
Show how you would accomplish the following syntheses.
(a) acetophenone → acetophenone cyanohydrin
273
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Domanda del libro di testo
Propose mechanisms for
(b) the base-catalyzed hydration of acetone to form acetone hydrate.
904
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Domanda del libro di testo
Show how you would accomplish the following syntheses.
b. cyclopentanecarbaldehyde → 2-cyclopentyl-2-hydroxyacetic acid
1059
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Domanda del libro di testo
Propose mechanisms for
(a) the acid-catalyzed hydration of chloral to form chloral hydrate.
868
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