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 Oxidative Cleavage

Organic Chemistry

10. Addition Reactions

Alkyne Oxidative Cleavage

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6:56 minutes

Problem 43a

Textbook Question

Deduce the structure of each compound from the information given. All unknowns in this problem have molecular formula C₈H₁₂.
(a) Upon catalytic hydrogenation, unknown W gives cyclooctane. Ozonolysis of W, followed by reduction with dimethyl sulfide, gives octanedioic acid, HOOC–(CH₂)₆–COOH. Draw the structure of W.

Verified step by step guidance

Step 1: Analyze the molecular formula C8H12. This indicates that the compound is unsaturated because the hydrogen count is less than the maximum possible for a saturated hydrocarbon (C8H18). The degree of unsaturation can be calculated using the formula: \( \text{Degree of Unsaturation} = \frac{2C + 2 - H}{2} \). Substituting \( C = 8 \) and \( H = 12 \), we find \( \text{Degree of Unsaturation} = \frac{2(8) + 2 - 12}{2} = 3 \). This means the compound has three degrees of unsaturation, which could correspond to rings or double bonds.

Step 2: Consider the information that catalytic hydrogenation of W gives cyclooctane. This suggests that W contains a single ring structure (cyclooctane is a saturated cyclic compound) and that the unsaturation in W is due to double bonds rather than additional rings.

Step 3: Examine the ozonolysis product. Ozonolysis cleaves double bonds and forms carbonyl-containing compounds. The product given is octanedioic acid, \( \text{HOOC-(CH2)6-COOH} \), which is a dicarboxylic acid with eight carbons. This indicates that W contains two double bonds, and their cleavage leads to the formation of the two carboxylic acid groups at the ends of the chain.

Step 4: Deduce the structure of W based on the above information. Since W has a single ring (cyclooctane after hydrogenation) and two double bonds, the structure of W must be a cyclooctadiene. The positions of the double bonds must be such that ozonolysis produces octanedioic acid. This implies that the double bonds are located opposite each other in the ring, leading to the cleavage of the ring into a linear dicarboxylic acid.

Step 5: Draw the structure of W. The structure is \( \text{1,5-cyclooctadiene} \), where the double bonds are at positions 1 and 5 of the cyclooctane ring. This arrangement satisfies the molecular formula, the degree of unsaturation, and the ozonolysis product.

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Key Concepts

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

Catalytic Hydrogenation

Catalytic hydrogenation is a chemical reaction that involves the addition of hydrogen (H2) to unsaturated organic compounds, typically in the presence of a catalyst such as palladium, platinum, or nickel. This process converts alkenes or alkynes into alkanes, effectively saturating the molecule. In the context of the question, the hydrogenation of compound W yielding cyclooctane indicates that W must contain a structure that can be fully saturated to form this cyclic alkane.

Ozonolysis

Ozonolysis is a reaction involving the cleavage of alkenes or alkynes using ozone (O3), resulting in the formation of carbonyl compounds such as aldehydes or ketones. The reaction typically proceeds through the formation of an ozonide intermediate, which is then reduced to yield the final products. In this case, the ozonolysis of compound W leading to octanedioic acid suggests that W contains a double bond that, when cleaved, produces the dicarboxylic acid structure.

Molecular Formula Interpretation

The molecular formula provides essential information about the number and types of atoms in a compound. For C8H12, the formula indicates that the compound contains eight carbon atoms and twelve hydrogen atoms, suggesting a degree of unsaturation. This unsaturation can be due to double bonds or rings in the structure. Understanding how to interpret this formula is crucial for deducing the possible structures of compound W, especially in relation to the reactions it undergoes.

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Related Practice

Textbook Question

Using cyclooctyne 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.)

(g) cyclooctane-1,2-dione

Textbook Question

(i)

Textbook Question

Predict the product(s) you would expect from treatment of each compound with (1) dilute, neutral KMnO₄ and (2) warm basic KMnO₄, then dilute acid.

(d) 2-methylhex-3-yne

Textbook Question

Predict the product(s) you would expect from treatment of each compound with (1) dilute, neutral KMnO₄ and (2) warm basic KMnO₄, then dilute acid.

(e) cyclodecyne

Textbook Question

Predict the product(s) you would expect from treatment of each compound with (1) dilute, neutral KMnO4 and (2) warm basic KMnO4, then dilute acid.

(b) hex-2-yne

Textbook Question

Predict the product(s) you would expect from treatment of each compound with (1) dilute, neutral KMnO₄ and (2) warm basic KMnO₄, then dilute acid.

(a) hex-1-yne

Textbook Question

Predict the product(s) you would expect from treatment of each compound with (1) dilute, neutral KMnO₄ and (2) warm basic KMnO₄, then dilute acid.

Textbook Question

Show how you would synthesize the following carboxylic acids, using the indicated starting materials.

(a) oct-4-yne → butanoic acid

(b) trans-cyclodecene → decanedioic acid

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