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

3. Acids and Bases

Ranking Acidity

Organic Chemistry

3. Acids and Bases

Ranking Acidity

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6:14 minutes

Problem 11b

Textbook Question

Ethanol, methylamine, and acetic acid are all amphoteric, reacting as either acids or bases depending on the conditions.

b. Rank ethanol, methylamine, and acetic acid in decreasing order of basicity. In each case, show the equation for the reaction with a generic acid (HA) to give the conjugate acid.

Verified step by step guidance

Identify the functional groups in each compound: Ethanol (CH3CH2OH) has a hydroxyl group, methylamine (CH3NH2) has an amino group, and acetic acid (CH3COOH) has a carboxylic acid group.

Understand the basicity of each functional group: Amines (like methylamine) are generally more basic than alcohols (like ethanol) and carboxylic acids (like acetic acid) because the lone pair on nitrogen is more available for protonation compared to the lone pairs on oxygen.

Write the reaction of each compound with a generic acid (HA) to form the conjugate acid: For ethanol, CH3CH2OH + HA → CH3CH2OH2+ + A-. For methylamine, CH3NH2 + HA → CH3NH3+ + A-. For acetic acid, CH3COOH + HA → CH3COOH2+ + A-.

Compare the stability of the conjugate acids: The conjugate acid of methylamine (CH3NH3+) is more stable than that of ethanol (CH3CH2OH2+) and acetic acid (CH3COOH2+), making methylamine the most basic.

Rank the compounds in decreasing order of basicity: Methylamine > Ethanol > Acetic Acid.

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Key Concepts

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

Amphoteric Compounds

Amphoteric compounds can act as both acids and bases depending on the environment. This dual behavior is crucial in acid-base chemistry, as it allows these substances to participate in various reactions. For example, ethanol can donate a proton (acting as an acid) or accept a proton (acting as a base), depending on the reactants present.

Basicity

Basicity refers to the ability of a substance to accept protons (H+) in a chemical reaction. In the context of the question, the basicity of ethanol, methylamine, and acetic acid can be compared by examining their structures and the stability of their conjugate acids. Methylamine, with its nitrogen atom, is generally more basic than ethanol and acetic acid due to the availability of a lone pair of electrons for protonation.

Conjugate Acids

A conjugate acid is formed when a base accepts a proton. Understanding the formation of conjugate acids is essential for ranking the basicity of the given compounds. For instance, when methylamine reacts with a generic acid (HA), it forms its conjugate acid (CH3NH3+), which can be compared to the conjugate acids of ethanol and acetic acid to determine their relative basicities.

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Related Practice

Textbook Question

The following compounds can all react as acids.

c. Rank the original compounds in order, from strongest acid to weakest acid.

Textbook Question

Consider the type of orbitals involved, and rank the following nitrogen compounds in order of decreasing basicity. 2. Rank the conjugate acids in order of increasing acidity. (Hint: These two orders should be the same!)

Textbook Question

Consider each pair of bases, and explain which one is more basic. Draw their conjugate acids, and show which one is a stronger acid.

(a)

(b)

Textbook Question

Write equations for the following acid–base reactions. Label the conjugate acids and bases, and show any inductive stabilization. Predict whether the equilibrium favors the reactants or products. Try to do this without using a table of pKa values, but if you need a hint, you can consult Appendix 4.

a. CH₃CH₂OH + CH₃NH⁻

b. F₃CCOONa + Br₃C—COOH

c. CH₃OH + H₂SO₄

Textbook Question

Ethanol, methylamine, and acetic acid are all amphoteric, reacting as either acids or bases depending on the conditions.

a. Rank ethanol, methylamine, and acetic acid in decreasing order of acidity. In each case, show the equation for the reaction with a generic base (B:⁻) to give the conjugate base.

Textbook Question

Which is a stronger acid?

c. <IMAGE>

d. CH₃CH₂CH₂OH or CH₃CH₂CH₂SH

Textbook Question

Which is a stronger acid?

Textbook Question

For each of the following compounds, indicate the atom that is protonated when an acid is added to a solution of the compound.

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