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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6:16 minutes

Problem 40b

Textbook Question

The following compound can become protonated on any of the three nitrogen atoms. One of these nitrogens is much more basic than the others, however.
b. Determine which nitrogen atom is the most basic.

Verified step by step guidance

Identify the three nitrogen atoms in the compound: Nitrogen 1 is bonded to an ethyl group and a hydrogen, Nitrogen 2 is part of an amide group, and Nitrogen 3 is part of an imine group.

Consider the electronic environment of each nitrogen atom. Nitrogen 1 is a secondary amine, Nitrogen 2 is an amide nitrogen, and Nitrogen 3 is an imine nitrogen.

Evaluate the basicity of each nitrogen. Basicity is influenced by the availability of the lone pair of electrons on the nitrogen to accept a proton.

Nitrogen 1, being part of a secondary amine, has its lone pair more available for protonation compared to Nitrogen 2 and Nitrogen 3. Amide nitrogen (Nitrogen 2) is less basic due to resonance delocalization of its lone pair with the carbonyl group. Imine nitrogen (Nitrogen 3) is also less basic due to the partial positive charge on the nitrogen from the double bond.

Conclude that Nitrogen 1 is the most basic nitrogen atom in the compound because its lone pair is not involved in resonance and is more available to accept a proton.

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Key Concepts

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

Basicity of Nitrogen Atoms

Basicity refers to the ability of a compound to accept protons (H+ ions). In nitrogen-containing compounds, the basicity is influenced by the availability of the lone pair of electrons on the nitrogen atom. The more available the lone pair, the stronger the base. In this case, the nitrogen atom's environment, including steric and electronic effects, will determine its basicity.

Steric Hindrance

Steric hindrance occurs when the spatial arrangement of atoms in a molecule prevents certain interactions, such as protonation. In the context of nitrogen atoms, if a nitrogen is surrounded by bulky groups, it may be less accessible for protonation, thus affecting its basicity. Understanding the spatial arrangement of the nitrogen atoms in the given compound is crucial for determining which is the most basic.

Resonance Effects

Resonance refers to the delocalization of electrons within a molecule, which can stabilize or destabilize certain structures. In nitrogen-containing compounds, resonance can affect the electron density on nitrogen atoms, influencing their basicity. If a nitrogen atom is involved in resonance with a carbonyl or other electronegative groups, it may be less basic due to reduced electron availability for protonation.

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Related Practice

Textbook Question

Which is a stronger base?

Textbook Question

Which is a stronger acid?

c. CH₃OCH₂CH₂CH₂OHorCH₃CH₂OCH₂CH₂OH

Textbook Question

The pK_a of ascorbic acid (vitamin C, page 55) is 4.17, showing that it is slightly more acidic than acetic acid (CH₃COOH, pK_a 4.74).

c. Compare the most stable conjugate base of ascorbic acid with the conjugate base of acetic acid, and suggest why these two compounds have similar acidities, even though ascorbic acid lacks the carboxylic acid (COOH) group.

Textbook Question

Rank the following acids in decreasing order of their acid strength. In each case, explain why the previous compound should be a stronger acid than the one that follows it.

Textbook Question

Choose the more basic member of each pair of isomers, and show why the base you chose is more basic.

(a)

(b)

Textbook Question

The following compounds are listed in increasing order of acidity. In each case, the most acidic proton is shown in red.

b. Explain why X is a stronger acid than W.

c. Explain why Y is a stronger acid than X.

d. Explain why Z is a stronger acid than Y.

Textbook Question

Choose the more acidic member of each pair of isomers, and show why the acid you chose is more acidic.

(a)