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

14. Synthetic Techniques

Retrosynthesis

Organic Chemistry

14. Synthetic Techniques

Retrosynthesis

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3:58 minutes

Problem 34e

Textbook Question

What reagents should be used to carry out the following syntheses?

Verified step by step guidance

Identify the starting material and the desired product for each transformation. The starting material is an alkyne (RC≡CH), and the products include alkenes, alkyl halides, and carbonyl compounds.

For the conversion of RC≡CH to RCH₂CH₃, use hydrogenation. The reagent needed is H₂ with a metal catalyst such as Pd/C or Pt.

To convert RC≡CH to RCH=CH₂, perform a partial hydrogenation. Use H₂ with a Lindlar catalyst to stop the reaction at the alkene stage.

For the transformation to RCHBrCH₃, use hydrohalogenation. The reagent required is HBr, which adds across the triple bond to form the bromoalkene.

To synthesize the carbonyl compounds, use hydration reactions. For example, to form RCOCH₃, use H₂O with a catalytic amount of H₂SO₄ and HgSO₄ to convert the alkyne to a ketone.

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Key Concepts

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

Alkyne Halogenation

Alkyne halogenation involves the addition of halogens (like Br2) to alkynes, resulting in the formation of dihaloalkenes or tetrahaloalkanes. This reaction typically proceeds through an electrophilic addition mechanism, where the triple bond of the alkyne acts as a nucleophile, attacking the halogen molecule. Understanding the regioselectivity and stereochemistry of these reactions is crucial for predicting the products.

Reagents for Synthesis

Choosing the correct reagents is essential for successful organic synthesis. In the context of alkyne halogenation, common reagents include halogens (Br2, Cl2) and solvents like carbon tetrachloride (CCl4) or dichloromethane (CH2Cl2). The choice of reagent can influence the reaction pathway and the final product, making it important to understand their roles in the reaction mechanism.

Electrophilic Addition Mechanism

The electrophilic addition mechanism is a fundamental reaction pathway in organic chemistry, particularly for unsaturated compounds like alkenes and alkynes. In this mechanism, an electrophile attacks the nucleophilic double or triple bond, leading to the formation of a more stable carbocation intermediate. This process is crucial for understanding how different reagents interact with alkynes to yield various products, as illustrated in the provided diagram.

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Related Practice

Textbook Question

How could the following compounds be prepared, using cyclohexene as a starting material?

Textbook Question

Using the given starting material, any necessary inorganic reagents and catalysts, and any carbon-containing compounds with no more than three carbons, indicate how each of the following compounds can be prepared:

Textbook Question

Which of the reactions cannot be used for the synthesis of isobutyl alcohol?

Textbook Question

For each synthesis, start with bromocyclohexane and predict the products. Assume that an excess of each reactant is added so that all possible reactions that can happen will happen.