Domanda del libro di testo
The introduction of elimination reactions provides a second way to synthesize alkynes in a two-step process starting with an alkene. Suggest a mechanism for both steps of this process.
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Ch. 12 - Substitution and Elimination: Reactions of Haloalkanes
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. 12 - Substitution and Elimination: Reactions of HaloalkanesProblema 61
Mullins 1st EditionCh. 12 - Substitution and Elimination: Reactions of HaloalkanesProblema 61Capitolo 11, Problema 61
In Chapter 10, you learned how to make an alkyne by acetylide alkylation with a 1° haloalkane. Suggest a mechanism by which this reaction occurs.
Guida verificata passo dopo passo1
Step 1: Begin by identifying the reactants involved in the acetylide alkylation reaction. The key components are the acetylide ion (a strong nucleophile) and the 1° haloalkane (a molecule containing a primary carbon bonded to a halogen). The acetylide ion is typically generated by deprotonating a terminal alkyne using a strong base such as NaNH₂.
Step 2: Recognize the type of reaction mechanism involved. This reaction proceeds via an SN2 (bimolecular nucleophilic substitution) mechanism because the 1° haloalkane is sterically unhindered, allowing the acetylide ion to attack the carbon bonded to the halogen directly.
Step 3: Describe the nucleophilic attack. The acetylide ion, which has a lone pair of electrons on the carbon, attacks the electrophilic carbon of the 1° haloalkane. This carbon is partially positive due to the electronegativity of the halogen atom, which withdraws electron density.
Step 4: Explain the leaving group departure. As the acetylide ion forms a new bond with the electrophilic carbon, the halogen atom (the leaving group) simultaneously departs, taking its bonding electrons with it. This ensures the reaction proceeds in a single concerted step characteristic of the SN2 mechanism.
Step 5: Highlight the product formation. The result of this reaction is a new alkyne with the acetylide group attached to the carbon chain of the original haloalkane. The halogen is released as a halide ion (e.g., Cl⁻, Br⁻, or I⁻), completing the reaction.
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Alkynes and Acetylide Ions
Alkynes are hydrocarbons containing at least one carbon-carbon triple bond. Acetylide ions, which are formed by deprotonating terminal alkynes, are strong nucleophiles that can react with electrophiles, such as haloalkanes. Understanding the structure and reactivity of acetylide ions is crucial for predicting the outcome of the alkylation reaction.
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Percorso guidato
3:39
Metal Ion Catalysis Concept 1
Nucleophilic Substitution Mechanism (SN2)
The SN2 mechanism is a type of nucleophilic substitution where the nucleophile attacks the electrophile from the opposite side of the leaving group, resulting in a concerted reaction. This mechanism is characteristic of primary haloalkanes, where steric hindrance is minimal, allowing for effective backside attack by the acetylide ion. Recognizing this mechanism is essential for understanding how the alkylation occurs.
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01:47Nucleophiles and Electrophiles can react in Substitution Reactions.
Formation of Alkynes via Alkylation
The process of forming alkynes through acetylide alkylation involves the reaction of an acetylide ion with a primary haloalkane, leading to the formation of a new carbon-carbon bond. This reaction is significant in organic synthesis as it allows for the construction of longer carbon chains and the introduction of functional groups. Familiarity with this transformation is key to grasping the overall synthesis of alkynes.
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09:11Alkyne Hydration
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Acetylide alkylation, from Assessment 12.61, fails to give the desired product with 2° haloalkanes. Why? What is the actual product of this reaction?
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Suggest a bromoalkane and the conditions necessary to produce the alkenes shown.
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For each pair, choose the haloalkane that would react most quickly in an Sₙ1 or E1 reaction.
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