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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2:17 minutes

Problem 42a

Textbook Question

Without using pK_a values, pick out the more reactive (least stable) base in each pair. Explain your answer.
(a)

Verified step by step guidance

Step 1: Understand the concept of base stability. A base's stability is influenced by factors such as electronegativity, resonance stabilization, inductive effects, and steric hindrance. Less stable bases are more reactive because they are more eager to accept protons.

Step 2: Analyze electronegativity. Bases with atoms that are less electronegative tend to be less stable because they hold onto electrons less tightly, making them more reactive.

Step 3: Consider resonance effects. If a base can delocalize its negative charge through resonance, it will be more stable. Bases without resonance stabilization are less stable and more reactive.

Step 4: Evaluate inductive effects. Electron-withdrawing groups near the negatively charged atom can stabilize the base by pulling electron density away. Bases lacking these stabilizing groups are less stable.

Step 5: Assess steric hindrance. Bulky bases may be less stable due to steric strain, which makes them more reactive. Compare the molecular structures of the bases in the pair to determine which one is less hindered and therefore less stable.

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Key Concepts

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

Acidity and Basicity

Acidity and basicity are fundamental concepts in organic chemistry that describe the tendency of a substance to donate protons (acids) or accept protons (bases). A stronger base is typically less stable because it has a greater tendency to react with protons, making it more reactive. Understanding the relative strengths of acids and bases helps in predicting the reactivity of different compounds.

Stability of Conjugate Bases

The stability of conjugate bases is crucial in determining the reactivity of bases. A less stable conjugate base corresponds to a stronger base, as it is more likely to accept a proton. Factors influencing stability include electronegativity, resonance, and inductive effects, which can either stabilize or destabilize the negative charge on the conjugate base.

Resonance and Charge Delocalization

Resonance refers to the delocalization of electrons across multiple structures, which can stabilize a molecule. In the context of bases, if a base can delocalize its negative charge through resonance, it becomes more stable and less reactive. Conversely, a base that cannot delocalize its charge effectively will be less stable and more reactive, making resonance a key factor in assessing base reactivity.

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Related Practice

Textbook Question

Without using pK_a values, pick out the least reactive (most stable) base in each pair. Explain your answer.

(a)

Textbook Question

Without using pK_a values, pick out the least reactive (most stable) base in each pair. Explain your answer.

(c)

Textbook Question

Which of the following indicated atoms would you expect to be most basic?

(a)

Textbook Question

Without using pK_a values, pick out the more acidic compound in each pair. Explain your answer.

(a)

Textbook Question

Tenormin, a member of the group of drugs known as beta-blockers, is used to treat high blood pressure and improve survival after a heart attack. It works by slowing down the heart to reduce its workload. Which atom in Tenormin is the most basic?

Textbook Question

A carboxylic acid ( pK_a = 5) is 10¹¹ times more acidic than an alcohol (pK_a = 16). Why?

Textbook Question

Compare the properties of propan-2-ol (I) and the hexafluoro analog (II).

(a) Compound II has almost triple the molecular weight of I, but II has a lower boiling point. Explain.

Textbook Question

e. Which has a greater Ka: cyclohexanol or phenol?

f. Which is a stronger acid: cyclohexanol or phenol?

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Without using pKa values, pick out the more reactive (least stable) base in each pair. Explain your answer. (a)

Key Concepts

Acidity and Basicity

Stability of Conjugate Bases

Resonance and Charge Delocalization

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Without using pK_a values, pick out the more reactive (least stable) base in each pair. Explain your answer.
(a)