Domanda del libro di testo
Provide the expected product for the reaction of each of the following alkenes with H2SO4 and H2O.
(d)
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Ch. 8 - Alkenes 1: Properties and Electrophilic Additions
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471
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TOC.tableOfContents
- 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 1: Properties and Electrophilic Additions158
- Ch. 9 - Alkenes 2: 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 1: Infrared Spectroscopy and Mass Spectrometry54
- Ch. 15 - Structural Identification 2: Nuclear Magnetic Resonance Spectroscopy93
- Ch. 16 - Metals in Organic Chemistry48
- Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones45
- Ch. 18 - Nucleophilic Acyl Substitution 1: Carboxylic Acids18
- Ch. 19 - Nucleophilic Acyl Substitution 2: Carboxylic Acid Derivatives39
- Ch. 20 - Enolates: Carbonyl Addition and Substitution13
- Ch. 21 - Conjugated Systems 1: Stability and Addition Reactions56
- Ch. 22 - Conjugated Systems 2: Pericyclic Reactions54
- Ch. 23 - Benzene 1: Aromatic Stability and Substitution Reactions64
- Ch. 24 - Benzene 2: 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: 9780137566471Non è quello che usi tu?Cambia libro di testo
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Mullins 1st EditionCh. 8 - Alkenes 1: Properties and Electrophilic AdditionsProblema 38
Mullins 1st EditionCh. 8 - Alkenes 1: Properties and Electrophilic AdditionsProblema 38Capitolo 7, Problema 38
Radical addition to alkenes is not effective for the synthesis of iodo- and chloroalkanes. Using your knowledge of the mechanism of this reaction, along with bond dissociation energies, explain why the radical additions of HI and HCl are not effective. (Assume ∆H = 65 kcal/ mol for the C–C π bond.)
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Radical addition to alkenes involves the formation of a radical intermediate, which is crucial for the propagation step in the reaction mechanism. The initiation step typically involves the homolytic cleavage of a bond to generate radicals.
In the case of HI and HCl, the bond dissociation energies (BDE) for H-I and H-Cl are relatively high compared to H-Br. This means that the energy required to break these bonds and form radicals is significant, making the initiation step less favorable.
The propagation step involves the addition of the radical to the alkene, forming a new radical. The stability of this new radical is important for the reaction to proceed. Iodine and chlorine radicals are less stable compared to bromine radicals, which affects the overall reaction kinetics.
The overall reaction must be exothermic for the radical addition to proceed effectively. The bond dissociation energy of the C-C π bond is given as 65 kcal/mol, which must be overcome. The energy released from forming new bonds must compensate for this, which is not the case for HI and HCl due to their high BDEs.
Therefore, the radical addition of HI and HCl to alkenes is not effective because the initiation step is energetically unfavorable, and the propagation step does not lead to a sufficiently stable radical intermediate, resulting in an overall endothermic process.
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Radical Addition Mechanism
Radical addition to alkenes involves the formation of radicals that initiate a chain reaction, adding across the double bond. The process typically requires a radical initiator, such as peroxides, to generate radicals from hydrogen halides. The stability of the radical intermediates and the energy required for bond formation are crucial factors in determining the feasibility of the reaction.
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Features of Addition Mechanisms.
Bond Dissociation Energy
Bond dissociation energy (BDE) is the energy required to break a bond homolytically, forming two radicals. In radical reactions, the BDE of the hydrogen-halide bond influences the reaction's progress. For HI and HCl, the BDEs are relatively low, making the formation of radicals less favorable compared to other halides like HBr, which has a more suitable BDE for radical formation.
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04:09How to calculate enthalpy using bond dissociation energies.
Thermodynamic Considerations
Thermodynamics play a critical role in radical reactions, where the overall enthalpy change (∆H) determines the reaction's favorability. The given ∆H for the C–C π bond is 65 kcal/mol, indicating the energy required to break the double bond. For HI and HCl, the radical addition is not thermodynamically favorable due to insufficient energy release from the formation of C–I and C–Cl bonds, making the reaction non-spontaneous.
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08:51Kinetic vs. Thermodynamic Control
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