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: minutes

Problem 16

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!)

Verified step by step guidance

Identify the type of nitrogen atom in each compound. The first image shows three compounds: a primary amine, an imine, and a nitrile. The second image shows a secondary amine, a nitrile, and another secondary amine.

Consider the hybridization of the nitrogen atom in each compound. In primary and secondary amines, the nitrogen is sp³ hybridized, in imines, the nitrogen is sp² hybridized, and in nitriles, the nitrogen is sp hybridized.

Understand that the basicity of nitrogen compounds is influenced by the availability of the lone pair of electrons on the nitrogen atom. The more available the lone pair, the more basic the compound.

Rank the compounds based on the hybridization and availability of the lone pair. sp³ hybridized nitrogen (amines) is more basic than sp² (imines), which is more basic than sp (nitriles). Therefore, primary and secondary amines are more basic than imines, which are more basic than nitriles.

For the conjugate acids, the order of increasing acidity is the reverse of the basicity order. The more basic the compound, the less acidic its conjugate acid. Therefore, the conjugate acids of nitriles are more acidic than those of imines, which are more acidic than those of amines.

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Key Concepts

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

Basicity and Acidity

Basicity refers to the ability of a compound to accept protons (H+), while acidity is the ability to donate protons. In organic chemistry, the strength of a base is often inversely related to the strength of its conjugate acid. Understanding these concepts is crucial for ranking compounds based on their basicity and acidity.

Orbital Hybridization

Orbital hybridization describes the mixing of atomic orbitals to form new hybrid orbitals that can influence the reactivity and properties of molecules. The type of hybridization (sp, sp2, sp3) affects the electron density around the nitrogen atom, which in turn impacts its basicity. Recognizing the hybridization of nitrogen in different compounds is essential for determining their relative basicity.

Resonance Effects

Resonance involves the delocalization of electrons across multiple structures, which can stabilize or destabilize a molecule. In the context of nitrogen compounds, resonance can affect the availability of the lone pair on nitrogen for protonation, thereby influencing basicity. Understanding how resonance structures contribute to the stability of conjugate acids is key to ranking their acidity.

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Related Practice

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)

(b)

(c)

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 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.

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.

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.

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