Textbook Question
For each pair of reactions, predict which will happen more quickly. [For (c) and (d), the more substituted carbocation is more stable due to hyperconjugation.]
(c)
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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 40a
Mullins 1st EditionCh. 5 - Chemical Reaction Analysis: Thermodynamics and KineticsProblem 40aChapter 4, Problem 40a
For each pair of reactions, predict which will happen more quickly.
[For (a) and (b), think about the stability of the bases involved.]
(a) 
Verified step by step guidance1
Step 1: Analyze the two reactions provided. In the first reaction, the base is an alkoxide ion (CH3CH2O⁻), which reacts with H⁺ to form an alcohol (CH3CH2OH). In the second reaction, the base is a carbanion (CH3CH2⁻), which reacts with H⁺ to form an alkane (CH3CH3).
Step 2: Consider the stability of the bases involved. Alkoxide ions (CH3CH2O⁻) are more stable than carbanions (CH3CH2⁻) because the negative charge on the oxygen atom is better stabilized due to its higher electronegativity compared to carbon.
Step 3: Recall that the stability of the base affects the rate of protonation. A more stable base will react more quickly with H⁺ because it is less reactive and more likely to accept a proton.
Step 4: Compare the two reactions. Since the alkoxide ion (CH3CH2O⁻) is more stable than the carbanion (CH3CH2⁻), the reaction involving the alkoxide ion will happen more quickly.
Step 5: Conclude that the first reaction (CH3CH2O⁻ + H⁺ → CH3CH2OH) will occur faster than the second reaction (CH3CH2⁻ + H⁺ → CH3CH3) due to the greater stability of the alkoxide ion compared to the carbanion.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Stability of Bases
The stability of a base is crucial in determining the rate of a reaction. A more stable base is less reactive and will typically lead to a slower reaction rate. Conversely, an unstable base is more reactive and can facilitate faster reactions. Understanding the factors that contribute to base stability, such as resonance and electronegativity, is essential for predicting reaction kinetics.
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The radical stability trend.
Reaction Mechanism
The reaction mechanism outlines the step-by-step process by which reactants are converted into products. It includes the formation and breaking of bonds, the transition states, and the intermediates involved. Analyzing the mechanism helps in understanding which reactions are favored based on the stability of the intermediates and transition states, thus influencing the overall reaction rate.
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Kinetics and Thermodynamics
Kinetics refers to the study of the rates of chemical reactions, while thermodynamics deals with the energy changes associated with reactions. A reaction may be thermodynamically favorable but kinetically slow if it has a high activation energy barrier. Understanding both concepts is vital for predicting which reaction will occur more quickly, as they provide insight into the energy landscape and the speed of the reaction pathway.
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Related Practice
Textbook Question
The following are all substitution reactions, two of which we study in later chapters. With no knowledge of mechanism, what would you expect the ratio of products to be for each reaction, based on a random statistical distribution?
(a) Replacing a hydrogen (H) with deuterium (D):
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Textbook Question
Using bond-dissociation energies, identify the most stable radical. Justify the difference in stability based on the structure.
(d) I• vs •OH
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Textbook Question
Using bond-dissociation energies, identify the most stable radical. Justify the difference in stability based on the structure.
(c)
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Textbook Question
The following are all substitution reactions, two of which we study in later chapters. With no knowledge of mechanism, what would you expect the ratio of products to be for each reaction, based on a random statistical distribution?
(a) Replacing a hydrogen (H) with chlorine (Cl):
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Textbook Question
Give the approximate bond-dissociation energy for each indicated bond.
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