Textbook Question
The following ethers are ranked according to their ability to form explosive peroxides. Explain this ranking based on your knowledge of the reaction mechanism.
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Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471
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Table of contents
- Ch. 2 - General Chemistry Translated: Finding the Electrons114
- Ch. 3 - Alkanes and Cycloalkanes: Properties and Conformational Analysis109
- Ch. 4 - Acids and Bases: Electron Flow144
- Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics118
- Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space112
- Ch. 7 - Principles of Green (Organic) Chemistry3
- Ch. 8 - Alkenes I: Properties and Electrophilic Additions158
- Ch. 9 - Alkenes II: Oxidation and Reduction150
- Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions101
- Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions108
- Ch. 12 - Substitution and Elimination: Reactions of Haloalkanes172
- Ch. 13 - Alcohols, Ethers and Related Compounds: Substitution and Elimination239
- Ch. 14 - Structural Identification I: Infrared Spectroscopy and Mass Spectrometry54
- Ch. 15 - Structural Identification II: Nuclear Magnetic Resonance Spectroscopy93
- Ch. 16 - Metals in Organic Chemistry48
- Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones45
- Ch. 18 - Nucleophilic Acyl Substitution I: Carboxylic Acids18
- Ch. 19 - Nucleophilic Acyl Substitution II: Carboxylic Acid Derivatives39
- Ch. 20 - Enolates: Carbonyl Addition and Substitution13
- Ch. 21 - Conjugated Systems I: Stability and Addition Reactions56
- Ch. 22 - Conjugated Systems II: Pericyclic Reactions54
- Ch. 23 - Benzene I: Aromatic Stability and Substitution Reactions64
- Ch. 24 - Benzene II: Reactions Influenced by the Aromatic Ring62
- Ch. 25 - Amines: Structure, Reactions, and Synthesis27
- Ch. 26 - Amino Acids, Proteins, and Peptide Synthesis9
- Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids54
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
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Mullins 1st EditionCh. 11 - Properties and Synthesis of Alkyl Halides: Radical ReactionsProblem 55
Mullins 1st EditionCh. 11 - Properties and Synthesis of Alkyl Halides: Radical ReactionsProblem 55Chapter 10, Problem 55
The solvent tetrahydrofuran (THF) is often sold with a small amount of BHT added. Provide a mechanism that explains why this might be so.
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Tetrahydrofuran (THF) is a cyclic ether that is prone to oxidation when exposed to air, forming peroxides. These peroxides can be hazardous as they are potentially explosive.
Butylated hydroxytoluene (BHT) is a common antioxidant added to THF to prevent the formation of peroxides. BHT acts by donating a hydrogen atom to free radicals, thus terminating the radical chain reaction that leads to peroxide formation.
The mechanism begins with the initiation step where THF is exposed to oxygen, forming a THF radical and a superoxide radical.
In the propagation step, the THF radical reacts with oxygen to form a peroxide radical. This peroxide radical can further react with THF to form more radicals, continuing the chain reaction.
BHT intervenes in the chain reaction by donating a hydrogen atom to the peroxide radical, converting it into a non-radical species and thus stopping the propagation of the radical chain reaction.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Tetrahydrofuran (THF)
Tetrahydrofuran (THF) is a cyclic ether commonly used as a solvent in organic chemistry due to its ability to dissolve a wide range of polar and nonpolar compounds. Its structure features a five-membered ring with four carbon atoms and one oxygen atom, which contributes to its unique properties, including low viscosity and high dielectric constant. Understanding THF's reactivity and stability is crucial for grasping why additives like BHT are used.
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Identification of polarity in solvents
BHT (Butylated Hydroxytoluene)
BHT, or Butylated Hydroxytoluene, is a synthetic antioxidant commonly added to various products to prevent oxidation. In the context of THF, BHT helps to inhibit the degradation of the solvent by scavenging free radicals that can form during storage or use. This preservation is essential for maintaining the solvent's effectiveness and preventing unwanted side reactions in chemical processes.
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05:49Mechanism of t-Butyl Ether Protecting Groups.
Free Radical Mechanism
The free radical mechanism involves the formation and reaction of free radicals, which are highly reactive species with unpaired electrons. In the presence of heat or light, THF can undergo autoxidation, leading to the generation of free radicals that can further react with the solvent, causing degradation. Understanding this mechanism is vital for explaining why BHT is added to THF, as it acts to stabilize the solvent by neutralizing these reactive intermediates.
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Related Practice
Textbook Question
Tributyltin hydride (Bu3SnH) is often used as a 'radical carrier' in radical reactions. Which bond would you expect to be weaker, Sn–H or C–H? How might this relate to radical stability? Explain your answer.
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Textbook Question
Provide the mechanism of the radical reactions shown.
(b)
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Textbook Question
If a small amount of a moderately nonpolar poisonous compound was added to a pond, why would it be safer to drink the water than it would be to eat the fish that live there?
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Textbook Question
Other molecules can be used as initiators in radical reactions. One such molecule is 2, 2'-azobisisobutyronitrile (AIBN). Show an arrow-pushing mechanism that rationalizes the formation of the following radical species. What are the driving forces of this reaction?
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Textbook Question
One danger associated with storing ether solvents is their tendency to form explosive peroxides when exposed to oxygen. Suggest a mechanism by which the hydroperoxide might form. You can assume the presence of X• to start the reaction.
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