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

1. A Review of General Chemistry

Degrees of Unsaturation

Organic Chemistry

1. A Review of General Chemistry

Degrees of Unsaturation

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4:37 minutes

Problem 1

Textbook Question

What is the molecular formula for a 5-carbon hydrocarbon with one $π$ bond and one ring?

Verified step by step guidance

Step 1: Understand the problem. A 5-carbon hydrocarbon with one π bond and one ring indicates that the molecule is cyclic and contains a double bond. This means it is an unsaturated hydrocarbon.

Step 2: Recall the general formula for hydrocarbons. Saturated hydrocarbons (alkanes) follow the formula C_nH_2n+2. However, the presence of a ring and a π bond reduces the number of hydrogens.

Step 3: Account for the ring. A ring introduces one degree of unsaturation, which reduces the hydrogen count by 2. The formula for a 5-carbon ring without any double bonds would be C₅H₁₀.

Step 4: Account for the π bond. A double bond introduces another degree of unsaturation, further reducing the hydrogen count by 2. Subtract 2 hydrogens from the formula in Step 3.

Step 5: Combine the information. The molecular formula is determined by considering the 5 carbons, the reduction in hydrogens due to the ring, and the reduction due to the π bond. Write the final molecular formula as C₅H₈.

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Key Concepts

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

Hydrocarbons

Hydrocarbons are organic compounds consisting entirely of hydrogen and carbon atoms. They can be classified into aliphatic (straight or branched chains) and aromatic (ring structures). Understanding the structure of hydrocarbons is essential for determining their molecular formulas and properties.

Unsaturation and π Bonds

Unsaturation in organic chemistry refers to the presence of double or triple bonds between carbon atoms, indicated by π (pi) bonds. Each π bond reduces the number of hydrogen atoms that can be attached to the carbon skeleton. In this case, the presence of one π bond suggests that the hydrocarbon is unsaturated, affecting its molecular formula.

Cyclic Compounds

Cyclic compounds are organic molecules that contain a ring structure. The presence of a ring can influence the molecular formula and the degree of unsaturation. For a hydrocarbon with a ring and a π bond, the ring structure contributes to the overall count of carbon and hydrogen atoms, which is crucial for deriving the correct molecular formula.

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Related Practice

Textbook Question

Determine the degree of unsaturation and then draw possible structures for noncyclic compounds with the following molecular formulas:

b. C₃H₄

Textbook Question

Determine the degree of unsaturation and then draw possible structures for noncyclic compounds with the following molecular formulas:

a. C₃H₆

Textbook Question

What is the molecular formula for each of the following?

a. a 4-carbon hydrocarbon with two $π$ bonds and no rings

Textbook Question

What is the molecular formula for each of the following?

b. a 10-carbon hydrocarbon with one $π$ bond and 2 rings

Textbook Question

If a hydrocarbon has nine carbon atoms, three double bonds, and one ring, how many hydrogen atoms must it have?

Hint: If you prefer to use a formula, elements of unsaturation = 1/2(2C + 2 - H)

C = number of carbons

H = number of hydrogens

Textbook Question

Cholesterol, C₂₇H₄₆O, has only one pi bond. With no additional information, what else can you say about its structure?

Textbook Question

Calculate the number of elements of unsaturation implied by the molecular formula C₆H₁₂.

Hint: If you prefer to use a formula, elements of unsaturation = 1/2(2C + 2 - H)

C = number of carbons

H = number of hydrogens

Textbook Question

Calculate the index of hydrogen deficiency for the following molecular formulas and structures.

(c)

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What is the molecular formula for a 5-carbon hydrocarbon with one π\pi bond and one ring?

Key Concepts

Hydrocarbons

Unsaturation and π Bonds

Cyclic Compounds

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What is the molecular formula for a 5-carbon hydrocarbon with one $π$ bond and one ring?