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1. NaNH, 2 Br 3. H₂, Lindlar's catalyst

1. NaNH, 2 Br 3. H₂, Lindlar's catalyst

Chemistry
Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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**Organic Chemistry Reaction: Synthesis of Alkynes** **Objective:** Draw the major product of the following reaction. **Reaction Scheme:** 1. Reactant: Alkyne compound with an attached bromoalkane. 2. Reagents: - 1. NaNH₂ - 2. *No additional reagent listed here - implies continuation from step 1* - 3. H₂, Lindlar's catalyst **Mechanism Details:** 1. **Sodium Amide (NaNH₂):** Sodium amide (NaNH₂) is a strong base and is used to deprotonate terminal alkynes, leading to the formation of an acetylide ion. 2. **Second Step (Connection of Bromoalkane):** The acetylide ion formed in the first step reacts with the bromoalkane (R-Br) through an S_N2 mechanism, resulting in coupling the acetylide ion with the alkyl halide. 3. **Hydrogenation with Lindlar's Catalyst (H₂, Lindlar's Catalyst):** The Lindlar's catalyst is a palladium catalyst poisoned with lead salts, resulting in the selective hydrogenation of alkynes to cis-alkenes. **Stepwise Description:** - The starting reactant is an alkyne with an adjacent bromoalkane. - Upon treatment with sodium amide (NaNH₂), the terminal hydrogen of the alkyne is abstracted, forming an acetylide ion. - This ion then undergoes an S_N2 reaction with the adjacent bromoalkane, forming a new carbon-carbon bond. - The combined product is finally treated with hydrogen gas (H₂) in the presence of Lindlar's catalyst which converts the alkyne to a cis-alkene. **Final Product:** - The major product of the reaction is a cis-alkene with the newly formed carbon-carbon bond between the positions initially occupied by the alkyne and the bromoalkane. **Graphical Representation:** The sequence in the reaction scheme indicates: Starting reactant: Alkyne with a structural representation shown. Reagents sequentially added as described above. Resulting molecule: Expected product, a specific structural depiction which should be a cis-alkene product. **Conclusion:** This reaction is an example of alkylation of the alkyne followed by selective
Transcribed Image Text:**Organic Chemistry Reaction: Synthesis of Alkynes** **Objective:** Draw the major product of the following reaction. **Reaction Scheme:** 1. Reactant: Alkyne compound with an attached bromoalkane. 2. Reagents: - 1. NaNH₂ - 2. *No additional reagent listed here - implies continuation from step 1* - 3. H₂, Lindlar's catalyst **Mechanism Details:** 1. **Sodium Amide (NaNH₂):** Sodium amide (NaNH₂) is a strong base and is used to deprotonate terminal alkynes, leading to the formation of an acetylide ion. 2. **Second Step (Connection of Bromoalkane):** The acetylide ion formed in the first step reacts with the bromoalkane (R-Br) through an S_N2 mechanism, resulting in coupling the acetylide ion with the alkyl halide. 3. **Hydrogenation with Lindlar's Catalyst (H₂, Lindlar's Catalyst):** The Lindlar's catalyst is a palladium catalyst poisoned with lead salts, resulting in the selective hydrogenation of alkynes to cis-alkenes. **Stepwise Description:** - The starting reactant is an alkyne with an adjacent bromoalkane. - Upon treatment with sodium amide (NaNH₂), the terminal hydrogen of the alkyne is abstracted, forming an acetylide ion. - This ion then undergoes an S_N2 reaction with the adjacent bromoalkane, forming a new carbon-carbon bond. - The combined product is finally treated with hydrogen gas (H₂) in the presence of Lindlar's catalyst which converts the alkyne to a cis-alkene. **Final Product:** - The major product of the reaction is a cis-alkene with the newly formed carbon-carbon bond between the positions initially occupied by the alkyne and the bromoalkane. **Graphical Representation:** The sequence in the reaction scheme indicates: Starting reactant: Alkyne with a structural representation shown. Reagents sequentially added as described above. Resulting molecule: Expected product, a specific structural depiction which should be a cis-alkene product. **Conclusion:** This reaction is an example of alkylation of the alkyne followed by selective
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