Textbook Question
The reaction of tert-butyl chloride with methanol
is found to follow the rate equation
rate = kr[(CH3)3C—Cl]
a. What is the kinetic order with respect to tert-butyl chloride?
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Ch.4 - The Study of Chemical Reactions
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 4, Problem 9a
a. Propose a mechanism for the free-radical chlorination of ethane,
Verified step by step guidance1
Step 1: Initiation - The process begins with the homolytic cleavage of the Cl-Cl bond under the influence of UV light (hv). This generates two chlorine radicals (Cl•). The reaction can be represented as:
Step 2: Propagation - In the first propagation step, a chlorine radical abstracts a hydrogen atom from ethane (CH3—CH3), forming a methyl radical (CH3—CH2•) and HCl. The reaction can be represented as:
Step 3: Propagation - In the second propagation step, the methyl radical reacts with another Cl2 molecule, forming the chlorinated product (CH3—CH2Cl) and regenerating a chlorine radical. The reaction can be represented as:
Step 4: Termination - The reaction can terminate when two radicals combine to form a stable molecule. For example, two chlorine radicals can combine to regenerate Cl2, or a methyl radical can combine with a chlorine radical to form CH3—CH2Cl. These termination steps reduce the number of radicals in the system.
Step 5: Summary - The overall reaction involves the conversion of ethane (CH3—CH3) and chlorine (Cl2) into chloroethane (CH3—CH2Cl) and HCl, with the mechanism proceeding through initiation, propagation, and termination steps. The free-radical mechanism is driven by the generation and interaction of reactive radical species.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Free Radical Mechanism
The free radical mechanism involves a series of steps where free radicals are generated and react with other molecules. In the case of chlorination, the process typically includes initiation, propagation, and termination steps. Initiation generates free radicals from chlorine molecules, propagation involves the reaction of these radicals with ethane to form chlorinated products, and termination occurs when two radicals combine to form a stable molecule.
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Chlorination of Alkanes
Chlorination of alkanes is a substitution reaction where hydrogen atoms in an alkane are replaced by chlorine atoms. This reaction is facilitated by the presence of light (hv) or heat, which provides the energy needed to break the Cl-Cl bond, generating chlorine radicals. The resulting chlorinated products can vary based on the number of hydrogen atoms replaced and the reaction conditions.
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Selectivity in Radical Reactions
Selectivity in radical reactions refers to the preference of radicals to abstract certain hydrogen atoms over others, leading to different products. In the case of ethane, the formation of primary versus secondary radicals can influence the distribution of chlorinated products. The stability of the resulting radical intermediates plays a crucial role in determining which hydrogen atoms are more likely to be replaced during the chlorination process.
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Related Practice
Textbook Question
b. Calculate ΔH° for each step in this reaction.
c. Calculate the overall value of ΔH° for this reaction.
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Textbook Question
For each reaction, estimate whether ΔS° for the reaction is positive, negative, or impossible to predict.
(a)
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Textbook Question
a. Using bond-dissociation enthalpies from Table 4-2. (page 167), calculate the heat of reaction for each step in the free-radical bromination of methane
b. Calculate the overall heat of the reaction.
Textbook Question
For each reaction, estimate whether ΔS° for the reaction is positive, negative, or impossible to predict.
(c)
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Textbook Question
For each reaction, estimate whether ΔS° for the reaction is positive, negative, or impossible to predict.
(b)
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