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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3:51 minutes

Problem 34a,b

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.
a.
b.

Verified step by step guidance

Step 1: Analyze the structure of compound A. It contains a carbonyl group (C=O) and an ether group (-O-). The oxygen atoms in these functional groups are potential sites for protonation because they have lone pairs of electrons that can interact with a proton (H⁺).

Step 2: Determine which oxygen atom in compound A is more likely to be protonated. The carbonyl oxygen is more electronegative and has a higher electron density compared to the ether oxygen. Additionally, protonation of the carbonyl oxygen leads to resonance stabilization, making it the preferred site for protonation.

Step 3: Analyze the structure of compound B. It contains a carbonyl group (C=O) and an amine group (-NH). Both the oxygen in the carbonyl group and the nitrogen in the amine group are potential sites for protonation due to their lone pairs of electrons.

Step 4: Compare the likelihood of protonation for the oxygen and nitrogen atoms in compound B. The nitrogen atom in the amine group is more basic than the oxygen atom in the carbonyl group, meaning it is more likely to accept a proton. Protonation of the nitrogen atom does not disrupt resonance, making it the preferred site for protonation.

Step 5: Summarize the findings. In compound A, the carbonyl oxygen is protonated when an acid is added. In compound B, the nitrogen in the amine group is protonated when an acid is added.

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Key Concepts

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

Protonation

Protonation is the addition of a proton (H⁺) to a molecule, which can significantly alter its chemical properties. In organic chemistry, understanding which atom is protonated helps predict the behavior of the compound in acidic conditions. Typically, protonation occurs at sites with high electron density, such as lone pairs on nitrogen or oxygen atoms.

Acidity and Basicity

Acidity refers to the ability of a compound to donate protons, while basicity is the ability to accept protons. The strength of an acid is often determined by the stability of its conjugate base after proton donation. In the context of the given compounds, identifying the most basic site will indicate where protonation is likely to occur when an acid is added.

Resonance Stabilization

Resonance stabilization occurs when a molecule can be represented by multiple valid Lewis structures, leading to increased stability. In the context of protonation, resonance can influence which atom is more favorable for protonation, as the resulting cation may be stabilized by delocalization of charge. This concept is crucial for predicting the outcome of acid-base reactions in organic compounds.

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Related Practice

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?

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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.

Textbook Question

Rank the carbanions shown in the margin from most basic to least basic.

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Textbook Question

b. How does the presence of an electronegative substituent such as Cl affect the acidity of a carboxylic acid?

c. How does the location of the substituent affect the acidity of the carboxylic acid?

Textbook Question

Explain the relative acidities.

CH₂═CHCH₂OH, CH₃CH₂CH₂OH, HC≡CCH₂OH

Textbook Question

Using the table of pK_a values given in [Appendix I] , answer the following:

d. Which is more electronegative: an sp³ oxygen or an sp² oxygen?

e. Which compounds demonstrate that the relative electronegativities of a hybridized nitrogen atom are sp > sp² > sp³?

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

Key Concepts

Protonation

Acidity and Basicity

Resonance Stabilization

Watch next

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