Textbook Question
The radical fluorination of 2-methyl propane resulted in a 14:86 ratio of products.
(a) On the basis of this ratio, calculate the relative reactivity of 1° and 3° C―H bonds in the radical fluorination.
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Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics
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. 5 - Chemical Reaction Analysis: Thermodynamics and KineticsProblem 46a
Mullins 1st EditionCh. 5 - Chemical Reaction Analysis: Thermodynamics and KineticsProblem 46aChapter 4, Problem 46a
Predict the major monohalogenation product(s) of the following reactions. Indicate whether you think the reaction will be selective and justify your position.
(a) 
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Step 1: Understand the concept of monohalogenation. Monohalogenation involves the substitution of one hydrogen atom in a molecule with a halogen atom (e.g., Cl, Br). This typically occurs via a radical mechanism when halogens react with alkanes under UV light or heat.
Step 2: Analyze the structure of the given molecule. Identify all types of hydrogen atoms present (e.g., primary, secondary, tertiary) and their relative positions in the molecule. This is crucial because the stability of the resulting radical intermediate determines the selectivity of the reaction.
Step 3: Recall the principle of radical stability. Tertiary radicals are more stable than secondary radicals, which are more stable than primary radicals. This stability influences the likelihood of halogenation at specific positions in the molecule.
Step 4: Predict the major product(s) based on the most stable radical intermediate. The halogen will preferentially replace a hydrogen atom at the position that forms the most stable radical. If multiple positions lead to radicals of similar stability, the reaction may be less selective, and multiple products may form.
Step 5: Justify the selectivity of the reaction. If the molecule has a clear preference for forming a specific radical (e.g., due to tertiary hydrogens), the reaction will be selective. If the molecule has hydrogens of similar reactivity, the reaction will be less selective, leading to a mixture of products.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Monohalogenation
Monohalogenation refers to the substitution reaction where one hydrogen atom in an organic compound is replaced by a halogen atom (such as Cl, Br, I, or F). This process typically occurs in alkanes and can be initiated by heat or light, leading to the formation of haloalkanes. Understanding the mechanism of this reaction is crucial for predicting the products formed.
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03:09
Acid Catalyzed
Selectivity in Halogenation
Selectivity in halogenation describes the preference of a halogen to replace certain hydrogen atoms over others in a molecule. Factors influencing selectivity include the type of halogen used, the structure of the alkane (e.g., primary, secondary, or tertiary), and the reaction conditions. For example, bromination is generally more selective than chlorination due to the stability of the radical intermediates formed during the reaction.
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03:45Halogenation Mechanism
Radical Mechanism
The radical mechanism is a key pathway in halogenation reactions, involving the formation of free radicals. This mechanism consists of three steps: initiation (formation of radicals), propagation (reaction of radicals with the substrate), and termination (recombination of radicals). Understanding this mechanism helps in predicting the products and the selectivity of the reaction, as different radicals can lead to different outcomes.
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03:28The mechanism of Radical Polymerization.
Related Practice
Textbook Question
Through the course of this chapter, we have discussed only alkane chlorination and bromination, yet there are two other halogens we have not discussed.
(b) Is radical iodination a favorable reaction? Do you expect it to be selective? Show your calculations.
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Textbook Question
Predict the major monohalogenation product(s) of the following reactions. Indicate whether you think the reaction will be selective and justify your position.
(c)
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Textbook Question
For each of the following acid–base reactions, (i) predict which side of the reaction you expect to be favored. If a pKa is not one of the ten common ones we learned in Chapter 4, it will be given to you.
(a)
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Textbook Question
The radical fluorination of 2-methyl propane resulted in a 14:86 ratio of products.
(b) From the relative reactivity, calculate the difference in energy between the transition states of the first propagation steps leading to a 1° and 3° radical.
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Textbook Question
The following table of strain energies is associated with a variety of 1,2-gauche interactions. Use this table to answer the questions (i)–(iv).
For each of the bond rotations shown, (i) identify which you believe to be more stable, (ii) calculate ∆G°, (iii) calculate the equilibrium constant, and (iv) draw the transition state.
(c)
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