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Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives
Bruice - Organic Chemistry 8th Edition
Bruice8th EditionOrganic ChemistryISBN: 9780135213711Not the one you use?Change textbook
Chapter 17, Problem 13a(1)

Show how the following compounds can be prepared, using ethyne as one of the starting materials:
1. 1-pentyn-3-ol

Verified step by step guidance
1
Step 1: Begin with ethyne (C₂H₂) as the starting material. Perform a reaction with sodium amide (NaNH₂) to generate the acetylide ion (C≡C⁻), which is a strong nucleophile.
Step 2: Perform an alkylation reaction by reacting the acetylide ion with 1-bromopropane (CH₃CH₂CH₂Br). This will extend the carbon chain, forming 1-butyne (CH≡C-CH₂CH₂CH₃).
Step 3: To introduce the hydroxyl group (-OH) at the desired position, perform a hydroboration-oxidation reaction. First, react 1-butyne with a bulky borane reagent, such as disiamylborane [(sia)₂BH], to ensure anti-Markovnikov addition of the boron atom.
Step 4: Oxidize the organoborane intermediate using hydrogen peroxide (H₂O₂) in the presence of a base (e.g., NaOH). This will replace the boron atom with a hydroxyl group, yielding 1-pentyn-3-ol.
Step 5: Verify the structure of the product to ensure that the hydroxyl group is located on the third carbon of the pentynyl chain, confirming the synthesis of 1-pentyn-3-ol.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Ethyne as a Building Block

Ethyne, also known as acetylene, 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 more complex molecules. Understanding how to manipulate ethyne in synthetic pathways is crucial for preparing target compounds.
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Alkyne Reactions

Alkynes undergo a variety of reactions, including hydration, hydroboration, and oxidation. In the case of preparing 1-pentyn-3-ol, the hydration of an alkyne can be achieved through acid-catalyzed reactions, leading to the formation of alcohols. Familiarity with these reactions and their mechanisms is essential for constructing the desired compound from ethyne.
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Functional Group Transformation

Functional group transformations involve converting one functional group into another, which is a key strategy in organic synthesis. In this context, transforming an alkyne into an alcohol requires specific reagents and conditions. Understanding how to effectively perform these transformations is vital for synthesizing compounds like 1-pentyn-3-ol from ethyne.
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