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

Alkyne Hydroboration

Organic Chemistry

10. Addition Reactions

Alkyne Hydroboration

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2:27 minutes

Problem 20d

Textbook Question

What are products of the following reactions?
d.

Verified step by step guidance

Step 1: Identify the reaction type. This is a hydroboration-oxidation reaction of an alkyne. The reagents R₂BH/THF followed by HO⁻, H₂O₂, and H₂O indicate that the alkyne will undergo anti-Markovnikov addition to form an aldehyde or ketone.

Step 2: Analyze the structure of the starting alkyne. The molecule contains a terminal alkyne (triple bond at the end of the chain) with a methyl group attached to the second carbon.

Step 3: In the first step, R₂BH adds to the terminal alkyne in an anti-Markovnikov fashion. The boron atom attaches to the less substituted carbon of the triple bond, forming an organoborane intermediate.

Step 4: In the second step, the organoborane intermediate reacts with hydrogen peroxide (H₂O₂) in the presence of hydroxide ions (HO⁻). This oxidation step converts the boron group into a hydroxyl group (-OH), resulting in the formation of an aldehyde.

Step 5: The final product is an aldehyde with the hydroxyl group replacing the terminal alkyne. The structure of the product will be CH₃-CH₂-CHO (propanal).

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Key Concepts

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

Reaction Mechanisms

Understanding reaction mechanisms is crucial in organic chemistry as they describe the step-by-step process by which reactants transform into products. This includes identifying intermediates, transition states, and the movement of electrons. Familiarity with mechanisms helps predict the outcome of reactions and the stability of products formed.

Functional Groups

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. Recognizing functional groups is essential for predicting the behavior of organic compounds during reactions, as they dictate reactivity and the types of products formed.

Stereochemistry

Stereochemistry involves the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. It is important for understanding isomerism, where compounds with the same molecular formula can have different structures and properties. This concept is vital when determining the products of reactions, especially in cases involving chiral centers.

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Related Practice

Textbook Question

The following functional-group interchange is a useful synthesis of aldehydes.

(a) What reagents were used in this chapter for this transformation? Give an example to illustrate this method.

(b) This functional-group interchange can also be accomplished using the following sequence.

Propose mechanisms for these steps.

Textbook Question

For each of the following alkynes, draw the products obtained from (1) the acid-catalyzed addition of water (mercuric ion is added for part a) and from (2) hydroboration–oxidation:

a. 1-butyne

Textbook Question

What is the major product of the reaction of 1 mol of propyne with each of the following reagents?

e. aqueous H₂SO₄, HgSO₄

f. R₂BH in THF followed by H₂O₂/HO⁻/H₂O

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.

Textbook Question

What hydrocarbon would you use to prepare the organoboron compound in Problem 14?

Multiple Choice

Predict the major, organic product for the following reaction.

Textbook Question

Answer Problem 39, parts a–h, using 2-butyne as the starting material instead of propyne.

f. R₂BH in THF followed by H₂O₂/HO⁻ /H₂O

Textbook Question

Predict the major products of the following reactions.

d. trans-cyclodecene + peroxyacetic acid in acidic water

e. cis-cyclodecene + mCPBA in CH₂Cl₂, then dilute aqueous acid