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Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis
Bruice - Organic Chemistry 8th Edition
Bruice8th EditionOrganic ChemistryISBN: 9780135213711Not the one you use?Change textbook
Chapter 8, Problem 28d

How could the following compounds be synthesized from acetylene?
d.

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1
Step 1: Begin with acetylene (C≡CH), a simple alkyne. The goal is to transform this molecule into the target compound, which is 2,2-dichloro-3,3-dimethylbutane.
Step 2: Perform a reaction to convert acetylene into a substituted alkyne. React acetylene with methyl iodide (CH3I) in the presence of a strong base like sodium amide (NaNH2). This will yield propyne (CH≡CCH3).
Step 3: Carry out a second alkylation reaction to further substitute the alkyne. React propyne with another equivalent of methyl iodide (CH3I) in the presence of NaNH2 to form 2-butyne (CH3C≡CCH3).
Step 4: Hydrogenate the alkyne to form the corresponding alkane. Use a Lindlar catalyst for partial hydrogenation to form 2-butene (CH3CH=CHCH3), or use a standard catalyst like Pd/C for complete hydrogenation to form butane (CH3CH2CH2CH3).
Step 5: Add chlorine atoms to the molecule. React the alkane or alkene with chlorine gas (Cl2) under UV light or appropriate conditions to form the desired compound, 2,2-dichloro-3,3-dimethylbutane. Ensure the reaction conditions favor substitution at the correct positions.

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Key Concepts

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

Acetylene Reactivity

Acetylene (C2H2) is a simple alkyne that can undergo various reactions due to its triple bond. It can participate in addition reactions, where reagents add across the triple bond, and can also be used in coupling reactions to form larger carbon frameworks. Understanding the reactivity of acetylene is crucial for determining how to synthesize more complex compounds from it.
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Functional Group Transformations

Functional group transformations involve changing one functional group in a molecule to another, which is essential in organic synthesis. This concept is important when synthesizing compounds from acetylene, as it may require converting the alkyne into alcohols, aldehydes, or other functional groups through various reactions like hydroboration, oxidation, or halogenation.
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Synthetic Pathways

Synthetic pathways refer to the step-by-step methods used to construct a target molecule from simpler starting materials. In the context of synthesizing compounds from acetylene, it is important to outline a logical sequence of reactions that efficiently build the desired structure, taking into account the necessary reagents, conditions, and potential side reactions.
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