Textbook Question
Show how you would synthesize the following alcohol by adding Grignard reagents to ethylene oxide.
(c)
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Ch.10 - Structure and Synthesis of Alcohols
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 10, Problem 20a,b
Acetylide ions also add to ethylene oxide much like Grignard and organolithium reagents. Predict the products obtained by adding the following acetylide ions to ethylene oxide, followed by a dilute acid workup.
(a) HC≡C:–
(b) CH3CH2–C≡C:–
Verified step by step guidance1
Step 1: Understand the reaction mechanism. Acetylide ions are strong nucleophiles that attack the electrophilic carbon in ethylene oxide, opening the three-membered ring. This results in the formation of an alkoxide intermediate.
Step 2: Analyze the acetylide ions provided. In part (a), the acetylide ion is HC≡C⁻, and in part (b), the acetylide ion is CH₃CH₂C≡C⁻. These ions will act as nucleophiles in the reaction.
Step 3: Predict the intermediate formed after the nucleophilic attack. The acetylide ion attacks the less sterically hindered carbon of ethylene oxide, breaking the ring and forming a linear alkoxide intermediate. For part (a), the intermediate will have a terminal alkyne group, and for part (b), the intermediate will have a substituted alkyne group.
Step 4: Perform the acid workup. The alkoxide intermediate is protonated by dilute acid, converting it into an alcohol. The alcohol will be located on the carbon adjacent to the alkyne group.
Step 5: Write the general product structure. For part (a), the product will be HC≡C-CH₂CH₂OH. For part (b), the product will be CH₃CH₂C≡C-CH₂CH₂OH. These products are formed after the acid workup step.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Acetylide Ions
Acetylide ions are negatively charged species formed from terminal alkynes by deprotonation. They are strong nucleophiles, capable of attacking electrophilic centers, such as carbon atoms in epoxides. In this context, acetylide ions react with ethylene oxide to open the epoxide ring, leading to the formation of alcohols after subsequent acid workup.
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Ethylene Oxide Reactivity
Ethylene oxide is a three-membered cyclic ether that is highly reactive due to its strained ring structure. It can undergo nucleophilic attack at the less hindered carbon atom, leading to ring opening. This property makes it a suitable substrate for reactions with nucleophiles like acetylide ions, resulting in the formation of alcohols after hydrolysis.
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Dilute Acid Workup
A dilute acid workup is a common procedure in organic synthesis used to protonate and stabilize reaction products. After the nucleophilic addition of acetylide ions to ethylene oxide, the dilute acid helps to convert the alkoxide intermediate into the corresponding alcohol. This step is crucial for ensuring that the final product is in its stable, protonated form.
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Related Practice
Textbook Question
Show how you would synthesize the following compound from alkyl halides, vinyl halides, and aryl halides containing no more than six carbon atoms.
(c) trans-oct-3-ene
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Textbook Question
Show how you would synthesize the following compound from alkyl halides, vinyl halides, and aryl halides containing no more than six carbon atoms.
(a) octane
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Textbook Question
Show how you would synthesize the following compound from alkyl halides, vinyl halides, and aryl halides containing no more than six carbon atoms.
(d) cyclopentyl propyl ketone
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Textbook Question
A formate ester, such as ethyl formate, reacts with an excess of a Grignard reagent to give (after protonation) secondary alcohols with two identical alkyl groups.
(b) Show how you would use reactions of Grignard reagents with ethyl formate to synthesize the following secondary alcohols.
(i) pentan-3-ol
(ii) diphenylmethanol
(iii) trans,trans-nona-2,7-dien-5-ol
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Textbook Question
Show how you would synthesize the following alcohol by adding Grignard reagents to ethylene oxide.
(a) 2-phenylethanol