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

Equilibrium Constant

Organic Chemistry

3. Acids and Bases

Equilibrium Constant

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7:40 minutes

Problem 24c

Textbook Question

For the following acid–base reaction, (c) calculate the ratio of butan-2-ol to 2-butoxide.

Verified step by step guidance

Step 1: Identify the acid and base in the reaction. Butan-2-ol acts as the acid, and 2-butoxide acts as the conjugate base. This is an acid–base equilibrium reaction.

Step 2: Determine the pKa value of butan-2-ol. The pKa is a measure of the strength of the acid, and it is essential for calculating the equilibrium constant. Look up the pKa value in a reliable reference source.

Step 3: Use the Henderson-Hasselbalch equation to calculate the ratio of the acid (butan-2-ol) to its conjugate base (2-butoxide). The equation is:

pH = pKa + \log (\frac{[A-]}{[HA]})

, where [HA] is the concentration of butan-2-ol and [A⁻] is the concentration of 2-butoxide.

Step 4: Rearrange the Henderson-Hasselbalch equation to solve for the ratio of [HA] to [A⁻]. The ratio can be expressed as:

\frac{[HA]}{[A-]} = 10^{(pKa - pH)}

. This step requires knowing the pH of the solution.

Step 5: Plug in the values for pKa and pH into the equation to calculate the ratio. Ensure that the pH of the solution is provided or determined experimentally. The final ratio will indicate the relative concentrations of butan-2-ol and 2-butoxide in the equilibrium mixture.

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Key Concepts

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

Acid-Base Reactions

Acid-base reactions involve the transfer of protons (H+) between reactants. In organic chemistry, acids are proton donors, while bases are proton acceptors. Understanding the nature of the acids and bases involved is crucial for predicting the products and calculating equilibrium constants in these reactions.

Alcohols and Alkoxides

Butan-2-ol is a secondary alcohol, which can act as a weak acid, while 2-butoxide is its corresponding alkoxide, formed when the alcohol loses a proton. The relationship between alcohols and their alkoxide counterparts is essential for understanding their reactivity and the equilibrium established in acid-base reactions.

Equilibrium and Ratios

In acid-base reactions, the equilibrium constant (K) can be used to determine the ratio of products to reactants at equilibrium. This ratio is critical for calculating the concentrations of butan-2-ol and 2-butoxide in the reaction, allowing for a quantitative understanding of the reaction dynamics and the extent of proton transfer.

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Related Practice

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:

e. ⁺NH4 (pK_a= 9.4)

f. HC≡N (pK_a= 9.1)

Textbook Question

Indicate whether an alcohol (ROH) with a pK_a value of 15 has more charged or more neutral molecules in a solution with the pH values given in Problem 41.

1. pH = 1

2. pH = 3

3. pH = 5

Textbook Question

Indicate whether an alcohol (ROH) with a pK_a value of 15 has more charged or more neutral molecules in a solution with the pH values given in Problem 41.

3. pH = 7

4. pH = 10

5. pH = 13

Textbook Question

A naturally occurring amino acid such as alanine has a group that is a carboxylic acid and a group that is a protonated amine. The pK_a values of the two groups are shown.

d. Draw the structure of alanine in a solution at pH = 12.

Textbook Question

What percent of imidazole is protonated at physiological pH (7.4)?

Textbook Question

For the following acid–base pairs, (iii) predict the favored side of equilibrium; (iv) calculate K_eq;

(h)

Multiple Choice

Which of the following is a correct statement about the equilibrium constant (K) in a chemical reaction?

Multiple Choice

If a given acid/base reaction has a K_eq = 10²⁵, what does this mean about the stability of the molecules?

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