Textbook Question
Show reaction sequences (not detailed mechanisms) that explain these transformations:
(a)
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Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds
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
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Wade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblem 82b
Wade 9th EditionCh. 22 - Condensations and Alpha Substitutions of Carbonyl CompoundsProblem 82bChapter 22, Problem 82b
Show the structure of the compound that results from hydrolysis and decarboxylation of the product.
Verified step by step guidance1
Step 1: Analyze the reaction sequence. The first step involves the reaction of benzaldehyde with malonic ester in the presence of a base (NaOCH2CH3). This is a typical example of the Knoevenagel condensation, where the malonic ester acts as a nucleophile and forms a double bond with the benzaldehyde.
Step 2: Examine the product of the Knoevenagel condensation. The product is a compound with a benzene ring attached to a CH=C group, which is further connected to two ester groups (-COOCH2CH3). This intermediate is ready for hydrolysis and decarboxylation.
Step 3: Understand the hydrolysis step. Under acidic conditions (H3O+), the ester groups (-COOCH2CH3) are hydrolyzed to carboxylic acids (-COOH). This converts the intermediate into a compound with two carboxylic acid groups attached to the CH=C group.
Step 4: Decarboxylation occurs upon heating (Δ). One of the carboxylic acid groups is removed as CO2, leaving behind a single carboxylic acid group. This step simplifies the structure and results in the final product.
Step 5: The final structure is a compound with a benzene ring attached to a CH=CH group, which is further connected to a single carboxylic acid group (-COOH). This is the result of hydrolysis and decarboxylation of the intermediate.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Hydrolysis
Hydrolysis is a chemical reaction involving the breaking of a bond in a molecule using water. In organic chemistry, it often refers to the conversion of esters, amides, or other functional groups into their corresponding acids or alcohols. This process is crucial for understanding how complex molecules can be transformed into simpler ones, which is essential for analyzing reaction mechanisms.
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Decarboxylation
Decarboxylation is the process of removing a carboxyl group (-COOH) from a molecule, typically releasing carbon dioxide (CO2). This reaction is significant in organic chemistry as it often leads to the formation of alkanes or other hydrocarbons from carboxylic acids. Understanding decarboxylation is vital for predicting the products of reactions involving carboxylic acids and their derivatives.
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Reaction Mechanisms
Reaction mechanisms describe the step-by-step sequence of elementary reactions by which overall chemical change occurs. In organic chemistry, understanding the mechanism helps predict the products of reactions, including hydrolysis and decarboxylation. A clear grasp of mechanisms allows chemists to manipulate conditions to favor desired outcomes in synthetic pathways.
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Related Practice
Textbook Question
Many of the condensations we have studied are reversible. The reverse reactions are often given the prefix retro-, the Latin word meaning “backward.” Propose mechanisms to account for the following reactions.
(c)
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Textbook Question
Biochemists studying the structure of collagen (a fibrous protein in connective tissue) found cross-links containing α,β-unsaturated aldehydes between protein chains. Show the structures of the side chains that react to form these cross-links, and propose a mechanism for their formation in a weakly acidic solution.
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Textbook Question
Propose a mechanism for the following reaction.
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Textbook Question
Show reaction sequences (not detailed mechanisms) that explain these transformations:
(b)
1
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Textbook Question
(A true story.) Chemistry lab students added an excess of ethylmagnesium bromide to methyl furoate, expecting the Grignard reagent to add twice and form the tertiary alcohol. After water workup, they found that the product was a mixture of two compounds. One was the expected product having two ethyl groups, but the unexpected product had added three ethyl groups. Propose a mechanism to explain the formation of the unexpected product.
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