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

2. Molecular Representations

Intermolecular Forces

Organic Chemistry

2. Molecular Representations

Intermolecular Forces

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5:13 minutes

Problem 9a

Textbook Question

In Table 7.2, what is the smallest alkane, the smallest terminal alkene, and the smallest terminal alkyne that are liquids at room temperature, which is generally taken to be 20 °C to 25 °C?

Verified step by step guidance

Step 1: Understand the question. The problem asks for the smallest alkane, terminal alkene, and terminal alkyne that are liquids at room temperature (20 °C to 25 °C). This requires knowledge of the physical states of hydrocarbons and their boiling points.

Step 2: Recall the general trend in boiling points of hydrocarbons. As the molecular weight (or chain length) of hydrocarbons increases, their boiling points increase due to stronger London dispersion forces. Smaller hydrocarbons (with fewer carbons) tend to be gases at room temperature, while larger ones are liquids or solids.

Step 3: Identify the smallest alkane that is a liquid at room temperature. Alkanes are saturated hydrocarbons with the general formula \( C_nH_{2n+2} \). Use a reference table or boiling point data to find the smallest alkane with a boiling point above 20 °C but below 25 °C.

Step 4: Identify the smallest terminal alkene that is a liquid at room temperature. Terminal alkenes are unsaturated hydrocarbons with a double bond at the end of the chain, having the general formula \( C_nH_{2n} \). Again, consult boiling point data to find the smallest terminal alkene with a boiling point in the specified range.

Step 5: Identify the smallest terminal alkyne that is a liquid at room temperature. Terminal alkynes are unsaturated hydrocarbons with a triple bond at the end of the chain, having the general formula \( C_nH_{2n-2} \). Use boiling point data to determine the smallest terminal alkyne that is a liquid at 20 °C to 25 °C.

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Key Concepts

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

Alkanes

Alkanes are saturated hydrocarbons consisting only of carbon and hydrogen atoms, connected by single bonds. They follow the general formula CnH2n+2, where 'n' is the number of carbon atoms. The smallest alkane is methane (CH4), which is a gas at room temperature, but as the number of carbon atoms increases, alkanes can become liquids, with pentane (C5H12) being the smallest liquid alkane.

Alkenes

Alkenes are unsaturated hydrocarbons that contain at least one carbon-carbon double bond, following the general formula CnH2n. The smallest terminal alkene is ethylene (C2H4), which is a gas at room temperature. However, as the carbon chain length increases, alkenes can also exist as liquids, with 1-hexene (C6H12) being the smallest liquid terminal alkene.

Alkynes

Alkynes are unsaturated hydrocarbons characterized by at least one carbon-carbon triple bond, adhering to the general formula CnH2n-2. The smallest terminal alkyne is acetylene (C2H2), which is a gas at room temperature. As with alkenes, longer-chain alkynes can be liquids, with 1-butyne (C4H6) being the smallest liquid terminal alkyne.

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Related Practice

Textbook Question

Which has

i. the greater density: heptane or octane?

j. the higher boiling point: isopentyl alcohol or isopentylamine?

k. the higher boiling point: hexylamine or dipropylamine?

Textbook Question

Which of the preceding compounds forms hydrogen bonds with a solvent such as ethanol?

4. CH₃CH₂CH₂NHCH₃

5. CH₃CH₂CH₂COOH

6. CH₃CH₂CH₂CH₂F

Textbook Question

Explain why

a. H₂O (100 °C) has a higher boiling point than CH₃OH 165 °C2.

b. H₂O (100 °C) has a higher boiling point than NH₃ (-33 °C).

Textbook Question

Which has

a. the higher boiling point: 1-bromopentane or 1-bromohexane?

b. the higher boiling point: pentyl chloride or isopentyl chloride?

Textbook Question

N-Methylpyrrolidine has a boiling point of 81 °C, and piperidine has a boiling point of 106 °C.

c. N,N-Dimethylformamide has a boiling point of 150 °C, and N-methylacetamide has a boiling point of 206 °C, for a difference of 56 °C. Explain why these two nitrogen-containing isomers have a much larger boiling point difference than the two amine isomers. Also explain why these two amides have higher boiling points than any of the other four compounds shown (two amines, an ether, and an alcohol).

Textbook Question

For each pair of compounds, circle the compound you expect to have the higher boiling point. Explain your reasoning.

(d) HOCH₂—(CH₂)₄—CH₂OH or (CH₃)₃CCH(OH)CH₃

(e) (CH₃CH₂CH₂)₂NH or (CH₃CH₂)₃N

(f)

Textbook Question

Which of the following pure compounds can form hydrogen bonds? Which can form hydrogen bonds with water? Which ones do you expect to be soluble in water?

a. (CH₃CH₂)₂NH

b. (CH₃CH₂)₃N

c. CH₃CH₂CH₂OH

d. (CH₃CH₂CH₂)₂OH

Textbook Question

Contrary to expectation, the addition of more fluorines to ethane lowers the boiling point. Explain this phenomenon.

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