4. Explain why the pka values of the indicated hydrogen atoms change as they do for these three compounds jh fl f pka 10 pka-10 Ka-20

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**Question 4:**

Explain why the pKa values of the indicated hydrogen atoms change as they do for these three compounds.

---

**Diagram Explanation:**

The image shows three different organic compounds. Each compound has a hydrogen atom indicated, and its respective pKa value is provided.

1. **Compound 1:**
   - Structure: Alkane with a simple carbon chain
   - Indicated Hydrogen: Attached to a carbon in the chain
   - pKa = 50

2. **Compound 2:**
   - Structure: Ketone (carbonyl group present)
   - Indicated Hydrogen: Attached to a carbon adjacent to the carbonyl group
   - pKa = 20

3. **Compound 3:**
   - Structure: 1,3-Dicarbonyl compound (two carbonyl groups present)
   - Indicated Hydrogen: Attached to a carbon between the two carbonyl groups
   - pKa = 10

---

**Analysis:**

The decreasing pKa values reflect increasing acidity of the hydrogen atoms in the compounds. The differences arise due to the following reasons:

- **Inductive Effect:** The presence of electronegative atoms or groups (such as the carbonyl groups) pulls electron density away from the hydrogen, stabilizing the negative charge that results when the hydrogen ionizes.

- **Resonance Stabilization:** In compound 3, the ionized form of the hydrogen is stabilized by resonance between the two carbonyl groups, significantly lowering the pKa compared to compound 2.

- **Hybridization:** The hybridization of the carbon atom to which hydrogen is attached also affects acidity, with more s-character leading to stronger acids.

This detailed exploration helps students understand how structural features influence acidity in organic molecules.
Transcribed Image Text:**Question 4:** Explain why the pKa values of the indicated hydrogen atoms change as they do for these three compounds. --- **Diagram Explanation:** The image shows three different organic compounds. Each compound has a hydrogen atom indicated, and its respective pKa value is provided. 1. **Compound 1:** - Structure: Alkane with a simple carbon chain - Indicated Hydrogen: Attached to a carbon in the chain - pKa = 50 2. **Compound 2:** - Structure: Ketone (carbonyl group present) - Indicated Hydrogen: Attached to a carbon adjacent to the carbonyl group - pKa = 20 3. **Compound 3:** - Structure: 1,3-Dicarbonyl compound (two carbonyl groups present) - Indicated Hydrogen: Attached to a carbon between the two carbonyl groups - pKa = 10 --- **Analysis:** The decreasing pKa values reflect increasing acidity of the hydrogen atoms in the compounds. The differences arise due to the following reasons: - **Inductive Effect:** The presence of electronegative atoms or groups (such as the carbonyl groups) pulls electron density away from the hydrogen, stabilizing the negative charge that results when the hydrogen ionizes. - **Resonance Stabilization:** In compound 3, the ionized form of the hydrogen is stabilized by resonance between the two carbonyl groups, significantly lowering the pKa compared to compound 2. - **Hybridization:** The hybridization of the carbon atom to which hydrogen is attached also affects acidity, with more s-character leading to stronger acids. This detailed exploration helps students understand how structural features influence acidity in organic molecules.
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