Textbook Question
Using any necessary inorganic reagents, show how you would convert acetylene and isobutyl bromide to
(b) (±)-2,7-dimethyloctane-4,5-diol.
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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 42a
Using any necessary inorganic reagents, show how you would convert acetylene and isobutyl bromide to
(a) meso-2,7-dimethyloctane-4,5-diol, (CH3)2CHCH2CH(OH)CH(OH)CH2CH(CH3)2.
Verified step by step guidance1
Step 1: Deprotonate acetylene (C₂H₂) using a strong base such as sodium amide (NaNH₂) to generate the acetylide ion (C≡C⁻). This ion is a strong nucleophile and will be used in the next step.
Step 2: Perform an alkylation reaction by reacting the acetylide ion with isobutyl bromide ((CH₃)₂CHCH₂Br). This will result in the formation of 2-methyl-1-butyne ((CH₃)₂CHCH₂C≡CH).
Step 3: Perform a second alkylation reaction. Deprotonate the terminal alkyne in 2-methyl-1-butyne using NaNH₂ to form another acetylide ion. Then react this ion with another equivalent of isobutyl bromide to form 2,7-dimethyloct-3-yne ((CH₃)₂CHCH₂C≡CCH₂CH(CH₃)₂).
Step 4: Reduce the triple bond in 2,7-dimethyloct-3-yne to a cis-alkene using Lindlar's catalyst. This will yield cis-2,7-dimethyloct-3-ene ((CH₃)₂CHCH₂CH=CHCH₂CH(CH₃)₂).
Step 5: Perform a syn-dihydroxylation of the cis-alkene using reagents such as osmium tetroxide (OsO₄) followed by hydrogen peroxide (H₂O₂). This will add hydroxyl groups (-OH) to the 4th and 5th carbons, resulting in meso-2,7-dimethyloctane-4,5-diol ((CH₃)₂CHCH₂CH(OH)CH(OH)CH₂CH(CH₃)₂).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Alkyne Reactivity
Acetylene is a simple alkyne that can undergo various reactions, including hydrogenation and nucleophilic addition. Understanding the reactivity of alkynes is crucial for converting them into more complex molecules. In this case, acetylene can be transformed into a more functionalized compound through reactions with inorganic reagents, which can facilitate the formation of alcohols in the final product.
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09:11
Alkyne Hydration
Nucleophilic Substitution
Nucleophilic substitution is a fundamental reaction mechanism in organic chemistry where a nucleophile replaces a leaving group in a molecule. In this question, isobutyl bromide serves as a substrate for nucleophilic attack, which is essential for forming the desired alcohols in the final product. Understanding the conditions that favor either SN1 or SN2 mechanisms will help in predicting the outcome of the reaction.
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01:47Nucleophiles and Electrophiles can react in Substitution Reactions.
Stereochemistry
Stereochemistry involves the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. The target compound, meso-2,7-dimethyloctane-4,5-diol, has specific stereochemical requirements, including the presence of chiral centers and a plane of symmetry. Recognizing how to control stereochemistry during synthesis is vital for achieving the correct configuration in the final product.
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Related Practice
Textbook Question
The following functional-group interchange is a useful synthesis of aldehydes.
(c) Explain why a nucleophilic reagent such as ethoxide adds to an alkyne more easily than it adds to an alkene.
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Textbook Question
Deduce the structure of each compound from the information given. All unknowns in this problem have molecular formula C8H12.
(a) Upon catalytic hydrogenation, unknown W gives cyclooctane. Ozonolysis of W, followed by reduction with dimethyl sulfide, gives octanedioic acid, HOOC–(CH2)6–COOH. Draw the structure of W.
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Textbook Question
Show how you would convert the following starting materials into the target compound. You may use any additional reagents you need.
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Textbook Question
The following functional-group interchange is a useful synthesis of aldehydes.
(a) What reagents were used in this chapter for this transformation? Give an example to illustrate this method.
(b) This functional-group interchange can also be accomplished using the following sequence.
Propose mechanisms for these steps.
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Textbook Question
Deduce the structure of each compound from the information given. All unknowns in this problem have molecular formula C8H12.
(c) Upon catalytic hydrogenation, unknown Y gives cyclooctane. Ozonolysis of Y, followed by reduction with dimethyl sulfide, gives a three-carbon dialdehyde and a five-carbon dialdehyde. Draw the structure of Y.
(d) Upon catalytic hydrogenation, unknown Z gives cis-bicyclo[4.2.0]octane. Ozonolysis of Z, followed by reduction with dimethyl sulfide, gives a cyclobutane with a three-carbon aldehyde (–CH2–CH2–CHO) group on C1 and a one-carbon aldehyde (–CHO) group on C2. Draw the structure of Z.
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