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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3:46 minutes

Problem 41a

Textbook Question

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

Verified step by step guidance

Step 1: Understand the concept of acidity. Acidity in organic compounds is determined by the ability of a molecule to donate a proton (H⁺). The stability of the conjugate base formed after losing the proton plays a key role in determining acidity.

Step 2: Analyze the structural features of the compounds in the pair. Look for factors such as electronegativity, resonance stabilization, inductive effects, and hybridization of the atom bonded to the acidic proton.

Step 3: Consider electronegativity. A proton attached to a more electronegative atom is more acidic because the electronegative atom stabilizes the negative charge on the conjugate base.

Step 4: Evaluate resonance effects. If the conjugate base can delocalize its negative charge through resonance, the compound is more acidic. Compare the resonance structures of the conjugate bases of the two compounds.

Step 5: Examine inductive effects and hybridization. Electron-withdrawing groups near the acidic proton increase acidity by stabilizing the conjugate base through inductive effects. Additionally, a proton attached to an sp-hybridized atom is more acidic than one attached to an sp² or sp³ atom due to the higher electronegativity of sp-hybridized atoms.

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Key Concepts

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

Acidity and Proton Donation

Acidity in organic chemistry refers to the ability of a compound to donate a proton (H⁺) to a base. The more readily a compound can lose a proton, the stronger its acidity. Factors influencing acidity include the stability of the resulting anion after proton donation and the electronegativity of atoms bonded to the acidic hydrogen.

Resonance Stabilization

Resonance stabilization occurs when a compound can be represented by multiple valid Lewis structures, allowing for the delocalization of electrons. This delocalization can stabilize the negative charge on the conjugate base formed after proton donation, making the original compound more acidic. Compounds with greater resonance stabilization of their conjugate bases are typically more acidic.

Inductive Effect

The inductive effect refers to the electron-withdrawing or electron-donating effects of substituents attached to a molecule. Electronegative atoms or groups can stabilize the negative charge of a conjugate base through the inductive effect, enhancing acidity. The presence of such groups near the acidic hydrogen can significantly influence the compound's acidity.

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Related Practice

Textbook Question

Identify the stronger acid in each pair. Explain your choice. Citing pK_a values is not an acceptable answer.

(a)

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 reactive (least stable) base 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.

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Without using pKa values, pick out the more acidic compound in each pair. Explain your answer. (a)

Key Concepts

Acidity and Proton Donation

Resonance Stabilization

Inductive Effect

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