Textbook Question
Starting with ethyne, describe how the following compounds can be synthesized:
a. (3S,4R)-4-bromo-3-hexanol and (3R,4S)-4-bromo-3-hexanol
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Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
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Bruice 8th EditionCh. 7 - The Reactions of Alkynes • An Introduction to Multistep SynthesisProblem 55b
Bruice 8th EditionCh. 7 - The Reactions of Alkynes • An Introduction to Multistep SynthesisProblem 55bChapter 8, Problem 55b
What stereoisomers are obtained from the following reactions?
b. 
Verified step by step guidance1
Step 1: Analyze the starting material, which is a terminal alkyne (CH3CH2C≡CCH2CH3). The triple bond is the reactive site in this molecule.
Step 2: The first reaction involves H2 with a Lindlar catalyst. This selectively reduces the alkyne to a cis-alkene. The Lindlar catalyst prevents further reduction to an alkane, ensuring the formation of a cis-alkene stereoisomer.
Step 3: The second reaction involves D2 with Pd/C. This is a catalytic hydrogenation reaction, but instead of H2, D2 is used. The alkene formed in the previous step undergoes syn-addition of deuterium atoms across the double bond, resulting in a fully saturated alkane with deuterium atoms added.
Step 4: Consider stereochemistry. The Lindlar catalyst ensures the cis configuration of the alkene intermediate. The syn-addition of D2 maintains the stereochemical integrity during the second step.
Step 5: The final product is a saturated alkane with deuterium atoms added. The stereoisomers obtained depend on the spatial arrangement of substituents around the original triple bond and the cis-alkene intermediate.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Stereoisomerism
Stereoisomerism refers to the phenomenon where compounds have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of their atoms. This can lead to different physical and chemical properties. In organic chemistry, stereoisomers can be classified into two main types: geometric isomers (cis/trans) and optical isomers (enantiomers), which are crucial for understanding the outcomes of reactions involving chiral centers.
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Determining when molecules are stereoisomers.
Hydrogenation of Alkynes
Hydrogenation is a chemical reaction that involves the addition of hydrogen (H2) to an unsaturated compound, such as an alkyne. The use of a Lindlar catalyst allows for the selective partial hydrogenation of alkynes to cis-alkenes, while the use of Pd/C can lead to complete hydrogenation to alkanes. Understanding the conditions and catalysts used in hydrogenation is essential for predicting the stereochemical outcomes of the reaction.
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Lindlar Catalyst
The Lindlar catalyst is a palladium-based catalyst that is poisoned to selectively hydrogenate alkynes to cis-alkenes without further reducing them to alkanes. It is crucial in organic synthesis for controlling the degree of hydrogenation and achieving specific stereochemical configurations. Recognizing the role of the Lindlar catalyst helps in predicting the stereoisomers formed during the reaction process.
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Related Practice
Textbook Question
A chemist is planning to synthesize 3-octyne by adding 1-bromobutane to the product obtained from the reaction of 1-butyne with sodium amide. Unfortunately, however, he forgot to order 1-butyne. How else can he prepare 3-octyne?
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Textbook Question
Explain why, in hydroboration–oxidation, HO− and HOOH cannot be added until after the hydroboration reaction is over.
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Textbook Question
a. Explain why a single pure product is obtained from hydroboration–oxidation of 2-butyne, whereas two products are obtained from hydroboration–oxidation of 2-pentyne.
b. Name two other internal alkynes that yield only one product upon hydroboration–oxidation.
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Textbook Question
α-Farnesene is a dodecatetraene found in the waxy coating of apple skins. What is its systematic name? Include E and Z where necessary to indicate the configuration of the double bonds.
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Textbook Question
What stereoisomers are obtained from the following reactions?
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