Textbook Question
Show how the following ketones might be synthesized from the indicated acids, using any necessary reagents.
(a) propiophenone from propionic acid (using Friedel–Crafts acylation)
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Ch. 21 - Carboxylic Acid Derivatives
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 21, Problem 17b
Soap manufacturers always use base to hydrolyze fats, and never acid. Suggest two reasons that basic hydrolysis is preferred.
Verified step by step guidance1
Understand the process of hydrolysis: Hydrolysis of fats (triglycerides) involves breaking the ester bonds in the triglyceride molecule to produce glycerol and fatty acid salts. This can be done using either acidic or basic conditions.
Reason 1: In basic hydrolysis (saponification), the fatty acids produced are immediately converted into their salt form (soap) by reacting with the base. This is advantageous because the soap (fatty acid salts) is water-soluble and can be easily separated from the reaction mixture.
Reason 2: In acidic hydrolysis, the fatty acids remain in their protonated form, which are not water-soluble. This makes the separation process more difficult and less efficient compared to basic hydrolysis.
Additional consideration: Basic hydrolysis is generally faster and more efficient than acidic hydrolysis because the hydroxide ion (OH⁻) is a stronger nucleophile than water, facilitating the cleavage of the ester bonds in triglycerides.
Practical aspect: Bases like NaOH or KOH are cheaper, safer, and easier to handle compared to strong acids, making the process more cost-effective and industrially viable for soap production.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Saponification
Saponification is the chemical reaction between a fat or oil and a base, typically sodium hydroxide or potassium hydroxide, resulting in the formation of soap and glycerol. This process is essential in soap manufacturing, as it effectively breaks down triglycerides into fatty acid salts (soaps) and glycerin, making it a preferred method over acid hydrolysis.
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Mechanism
Alkaline Conditions
Basic conditions are more effective for hydrolyzing fats because they promote the complete conversion of triglycerides into soap. In alkaline environments, the reaction proceeds more efficiently, yielding higher soap yields compared to acidic conditions, which may lead to incomplete hydrolysis and the formation of free fatty acids instead of soap.
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Safety and Handling
Using a base for hydrolysis is generally safer in industrial settings compared to acids. Bases like sodium hydroxide are less corrosive to equipment and safer for workers when handled properly, while strong acids can pose significant health risks and require more stringent safety measures, making basic hydrolysis a more practical choice for soap manufacturers.
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Related Practice
Textbook Question
Propose a mechanism for the base-promoted hydrolysis of γ-butyrolactone:
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Textbook Question
Explain why we speak of acidic hydrolysis of an ester as acid-catalyzed, but of basic hydrolysis as base-promoted.
Textbook Question
Suppose we have some optically pure (R)-2-butyl acetate that has been 'labeled' with the heavy 18O isotope at one oxygen atom as shown.
(c) Explain how you would prove experimentally where the 18O label appears in the products. (18O is not radioactive.)
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Textbook Question
Suppose we have some optically pure (R)-2-butyl acetate that has been "labeled" with the heavy 18O isotope at one oxygen atom as shown.
(b) Repeat part (a) for the acid-catalyzed hydrolysis of this compound.
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Textbook Question
Draw the important resonance contributors for both resonance-stabilized cations (in brackets) in the mechanism for acid-catalyzed hydrolysis of an amide.
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