Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

10. Addition Reactions

Addition Reaction

Organic Chemistry

10. Addition Reactions

Addition Reaction

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4:14 minutes

Problem 57a

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

Verified step by step guidance

Step 1: Begin with ethyne (C₂H₂) and perform a hydroboration-oxidation reaction to convert it into an aldehyde. This involves first reacting ethyne with disiamylborane (a bulky borane reagent) to form an organoborane intermediate, followed by oxidation with hydrogen peroxide (H₂O₂) in a basic solution (NaOH). This will yield acetaldehyde (CH₃CHO).

Step 2: Perform a Grignard reaction to extend the carbon chain. React acetaldehyde with ethylmagnesium bromide (C₂H₅MgBr) to form 3-pentanol. This reaction involves the nucleophilic attack of the Grignard reagent on the carbonyl carbon of acetaldehyde, followed by protonation during the acidic workup.

Step 3: Protect the hydroxyl group of 3-pentanol to prevent it from reacting in subsequent steps. Use a protecting group such as a silyl ether (e.g., TBDMSCl) in the presence of a base like imidazole to form the protected alcohol.

Step 4: Perform a bromination reaction to introduce a bromine atom at the 4-position. Use N-bromosuccinimide (NBS) in the presence of light or a radical initiator to selectively brominate the 4-position of the alkane chain. This step generates a racemic mixture of (3S,4R)-4-bromo-3-hexanol and (3R,4S)-4-bromo-3-hexanol.

Step 5: Deprotect the hydroxyl group to regenerate the free alcohol. Use a fluoride source such as tetrabutylammonium fluoride (TBAF) to remove the silyl protecting group, yielding the desired compounds: (3S,4R)-4-bromo-3-hexanol and (3R,4S)-4-bromo-3-hexanol.

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Key Concepts

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

Alkyne Reactivity

Ethyne, or acetylene, is a simple alkyne that can undergo various reactions due to its triple bond. This reactivity allows for the formation of different functional groups through processes such as hydrogenation, halogenation, and nucleophilic addition. Understanding how alkynes react is crucial for synthesizing more complex molecules from simpler starting materials.

Stereochemistry

Stereochemistry involves the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In the synthesis of (3S,4R)- and (3R,4S)-4-bromo-3-hexanol, it is essential to consider the stereochemical configuration at the chiral centers. This understanding helps in predicting the outcomes of reactions and the formation of specific isomers.

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions are fundamental in organic chemistry, where a nucleophile replaces a leaving group in a molecule. In the synthesis of the target alcohols, nucleophilic substitution can be employed to introduce the bromine atom at the desired position. Mastery of this concept is vital for constructing complex organic molecules from simpler precursors.

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Related Practice

Textbook Question

Using 1,2-dimethylcyclohexene as your starting material, show how you would synthesize the following compounds. (Once you have shown how to synthesize a compound, you may use it as the starting material in any later parts of this problem.) If a chiral product is shown, assume that it is part of a racemic mixture.

(h)

Textbook Question

Show what products you would expect from the following metathesis reactions, using the Schrock or Grubbs catalysts.

(a)

Textbook Question

Show what products you would expect from the following metathesis reactions, using the Schrock or Grubbs catalysts.

(c)

Textbook Question

Show how you might use olefin metathesis to assemble the following alkenes from smaller units:

(a)

(b)

Multiple Choice

Predict the major organic product of the following reaction.

Textbook Question

Synthesize the following molecules beginning with only organic molecules containing three carbons or fewer.

(g)

Textbook Question

Using any necessary inorganic reagents, show how you would convert acetylene and isobutyl bromide to

(a) meso-2,7-dimethyloctane-4,5-diol, (CH₃)₂CHCH₂CH(OH)CH(OH)CH₂CH(CH₃)₂.

Textbook Question

Predict the products formed when CH₃CH₂–C≡C:^–Na⁺ reacts with the following compounds.

a. ethyl bromide

b. tert-butyl bromide

c. formaldehyde

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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

Key Concepts

Alkyne Reactivity

Stereochemistry

Nucleophilic Substitution Reactions

Watch next

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