Textbook Question
Write structural formulas for the following compounds (includes both old- and new-style names).
(d) cyclohexylacetylene
(e) 5-methyl-3-octyne
(f) trans-3,5-dibromocyclodecyne
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Ch.9 - Alkynes
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 9, Problem 25b
Develop syntheses for the following compounds, using acetylene and compounds containing no more than four carbon atoms as your organic starting materials.
(b) cis-1-ethyl-2-methylcyclopropane
Verified step by step guidance1
Start by recognizing that the target molecule, cis-1-ethyl-2-methylcyclopropane, is a cyclopropane derivative with specific substituents in a cis configuration. The synthesis will involve forming the cyclopropane ring and introducing the substituents in the correct stereochemistry.
Use acetylene as the starting material. Acetylene can be converted into ethylene (C₂H₄) through hydrogenation using a Lindlar catalyst to stop at the alkene stage. This ethylene will serve as a precursor for further reactions.
To introduce the ethyl group, perform a hydroboration-oxidation reaction on ethylene to form ethanol (C₂H₅OH). Then, convert ethanol into ethyl bromide (C₂H₅Br) using phosphorus tribromide (PBr₃). This ethyl bromide will be used as an alkylating agent.
To form the cyclopropane ring, use a Simmons-Smith reaction. React a suitable alkene (e.g., propene, which can be synthesized from acetylene) with diiodomethane (CH₂I₂) and a zinc-copper couple to generate the cyclopropane ring. Ensure that the substituents are introduced in a way that maintains the cis configuration.
Finally, introduce the methyl group at the appropriate position on the cyclopropane ring. This can be achieved by using a methylating agent, such as methyl iodide (CH₃I), in the presence of a strong base. Verify that the stereochemistry of the product is cis by considering the reaction conditions and mechanisms.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acetylene as a Building Block
Acetylene (C2H2) is a simple alkyne that serves as a versatile building block in organic synthesis. Its triple bond allows for various reactions, including addition reactions with electrophiles, which can lead to the formation of larger carbon frameworks. Understanding how to manipulate acetylene is crucial for constructing complex molecules from simpler precursors.
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Cyclopropane Structure and Reactivity
Cyclopropane is a three-membered carbon ring known for its unique angle strain due to the 60-degree bond angles. This strain makes cyclopropane and its derivatives reactive, allowing for ring-opening reactions and the formation of substituted cyclopropanes. Recognizing how to synthesize and modify cyclopropane derivatives is essential for creating compounds like cis-1-ethyl-2-methylcyclopropane.
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01:49General properties of cyclopropanation.
Stereochemistry in Organic Synthesis
Stereochemistry refers to the spatial arrangement of atoms in molecules and is critical in organic synthesis, especially for compounds with multiple stereocenters. The cis- and trans- configurations can significantly affect the properties and reactivity of a compound. Understanding stereochemical principles is vital for accurately synthesizing and characterizing compounds like cis-1-ethyl-2-methylcyclopropane.
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Related Practice
Textbook Question
Write structural formulas for the following compounds (includes both old- and new-style names).
(a) 2-octyne
(b) ethylisopentylacetylene
(c) ethynylbenzene
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Textbook Question
Develop syntheses for the following compounds, using acetylene and compounds containing no more than four carbon atoms as your organic starting materials.
(a) 3-methylnon-4-yn-3-ol (“3-ol” means there is an OH group on C3.)
Textbook Question
Oxidative cleavages can help to determine the positions of the triple bonds in alkynes.
(b) An unknown alkyne undergoes oxidative cleavage to give the following triacid plus one equivalent of propionic acid. Propose a structure for the alkyne.
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Textbook Question
Oxidative cleavages can help to determine the positions of the triple bonds in alkynes.
(a) An unknown alkyne undergoes oxidative cleavage to give adipic acid and two equivalents of acetic acid. Propose a structure for the alkyne.
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Textbook Question
Write structural formulas for the following compounds (includes both old- and new-style names).
g. 5,5-dibromo-4-phenylcyclooct-1-yne
h. (E)-6-ethyloct-2-en-4-yne
i.1,4-heptadiyne
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