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

Acid Base Equilibrium

Organic Chemistry

3. Acids and Bases

Acid Base Equilibrium

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3:13 minutes

Problem 42f

Textbook Question

Complete the following acid–base reactions. In each case, indicate whether the equilibrium favors the reactants or the products, and explain your reasoning.
(f) (CH₃)₃C–O^– + H₂O ⇌

Verified step by step guidance

Identify the acid and base on both sides of the reaction. In this case, (CH3)3C—O⁻ is the base, and H2O is the acid on the reactant side. On the product side, the conjugate acid of (CH3)3C—O⁻ is (CH3)3C—OH, and the conjugate base of H2O is OH⁻.

Determine the relative acid strengths of the acids involved. Compare the pKa values of H2O (as an acid) and (CH3)3C—OH. H2O has a pKa of approximately 15.7, while (CH3)3C—OH has a pKa of approximately 18.

Recall that the equilibrium of an acid-base reaction favors the side with the weaker acid and weaker base. Since (CH3)3C—OH has a higher pKa (weaker acid) compared to H2O, the equilibrium will favor the side with (CH3)3C—OH and OH⁻.

Write the products of the reaction: (CH3)3C—OH and OH⁻. The reaction can be represented as: (CH3)3C—O⁻ + H2O ⇌ (CH3)3C—OH + OH⁻.

Conclude that the equilibrium favors the products because the weaker acid (higher pKa) and weaker base are on the product side. This is consistent with the principle that equilibrium favors the formation of the weaker acid-base pair.

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Key Concepts

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

Acid-Base Theory

Acid-base theory explains the behavior of acids and bases in chemical reactions. According to the Brønsted-Lowry theory, acids are proton donors while bases are proton acceptors. In the given reaction, the tert-butoxide ion ((CH3)3C—O-) acts as a base by accepting a proton from water (H2O), which acts as an acid. Understanding this theory is crucial for predicting the direction of the equilibrium.

Equilibrium Position

The position of equilibrium in a chemical reaction indicates whether the reactants or products are favored. This is determined by the relative strengths of the acids and bases involved. In this case, if the resulting products are weaker acids and bases than the reactants, the equilibrium will favor the products. Conversely, if the reactants are stronger, the equilibrium will favor them.

pKa Values

pKa values are a quantitative measure of the strength of an acid in solution; lower pKa values indicate stronger acids. When analyzing acid-base reactions, comparing the pKa values of the acids and bases involved helps predict the direction of equilibrium. In this reaction, knowing the pKa of water and the conjugate acid formed will help determine whether the equilibrium favors the reactants or products.

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Related Practice

Textbook Question

Ethyne (HC≡CH) has a pK_a value of 25, water has a pK_a value of 15.7, and ammonia (NH3) has a pKa value of 36. Draw the equation, showing equilibrium arrows that indicate whether reactants or products are favored, for the acid–base reaction of ethyne with

a. HO^-.

Textbook Question

Given the data in Problem 47:

a. What pH would you make the water layer to cause the carboxylic acid to dissolve in the water layer and the amine to dissolve in the ether layer?

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.

j. CF₃CH₂O^– + FCH₂CH₂OH

Textbook Question

Complete the following acid–base reactions. In each case, indicate whether the equilibrium favors the reactants or the products, and explain your reasoning.

(g) KOH + CH₃CH₂OH ⇌

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 pK_a values, but if you need a hint, you can consult Appendix 4.

g. NaOCH₂CH₃ + Cl₂CHCH₂OH

h. H₂Se + NaNH₂

i. CH₃CHFCOOH + FCH₂CH₂COO^–

Textbook Question

For each of the following compounds (here shown in their acidic forms), write the form that predominates in a solution with a pH = 5.5:

c. H₃O⁺ (pK_a = −1.7)

d. HBr (pK_a = −9)

Textbook Question

Do the equilibria of the following acid–base reactions lie to the right or the left? (The pK_a of H2O2 is 11.6.)

HOOH + HO⁻⇌ HOO⁻+ H2O

RC☰CH + HOO⁻⇌ RC☰C⁻+ HOOH

Textbook Question

Using pK_a values for the conjugate acids of the bases on each side of the reaction arrow, identify which side of the equilibrium would be favored in the following hypothetical reactions.

(a)

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Complete the following acid–base reactions. In each case, indicate whether the equilibrium favors the reactants or the products, and explain your reasoning.(f) (CH3)3C–O– + H2O ⇌

Key Concepts

Acid-Base Theory

Equilibrium Position

pKa Values

Watch next

Complete the following acid–base reactions. In each case, indicate whether the equilibrium favors the reactants or the products, and explain your reasoning.
(f) (CH₃)₃C–O^– + H₂O ⇌