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Ch. 2 - Acids and Bases; Functional Groups
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Wade 9th EditionCh. 2 - Acids and Bases; Functional Groups문제 18
2장, 문제 18

Which is a stronger base: ethoxide ion or acetate ion? Give pKb values (without looking them up) to support your choice.

검증된 단계별 안내
1
Identify the conjugate acids of the given bases: Ethoxide ion (C₂H₅O⁻) is the conjugate base of ethanol (C₂H₅OH), and acetate ion (CH₃COO⁻) is the conjugate base of acetic acid (CH₃COOH).
Recall that the strength of a base is inversely related to the strength of its conjugate acid. A weaker conjugate acid corresponds to a stronger base.
Consider the acidity of the conjugate acids: Ethanol is a weaker acid compared to acetic acid. This is because ethanol lacks the resonance stabilization that acetic acid has, which makes acetic acid a stronger acid.
Since ethanol is a weaker acid, its conjugate base, the ethoxide ion, is a stronger base compared to the acetate ion.
Estimate the pKb values: Since ethoxide ion is a stronger base, it will have a lower pKb value compared to the acetate ion. The exact pKb values are not needed, but this reasoning supports the conclusion that ethoxide ion is the stronger base.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Acid-Base Strength

The strength of a base is determined by its ability to accept protons. A stronger base has a higher tendency to accept protons, which is often reflected in its pKb value. The lower the pKb, the stronger the base. Understanding this concept helps compare the basicity of ethoxide and acetate ions.
추천 영상:
2:50
Acid-Base Catalysis Concept 3

Resonance Stabilization

Resonance stabilization occurs when a molecule can delocalize electrons across multiple atoms, reducing its reactivity. Acetate ion is resonance-stabilized, making it less reactive and a weaker base compared to ethoxide ion, which lacks such stabilization. This concept is crucial for understanding why ethoxide is a stronger base.
추천 영상:
가이드 코스
03:43
The radical stability trend.

Inductive Effect

The inductive effect involves the transmission of charge through a chain of atoms in a molecule, affecting its acidity or basicity. In ethoxide ion, the electron-donating effect of the ethyl group increases electron density on the oxygen, enhancing its basicity. This concept helps explain the relative strength of ethoxide as a base compared to acetate.
추천 영상:
가이드 코스
01:47
Understanding the Inductive Effect.
관련 실천
교과서 질문

Consider the type of orbitals involved, and rank the following nitrogen compounds in order of decreasing basicity. 2. Rank the conjugate acids in order of increasing acidity. (Hint: These two orders should be the same!)

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교과서 질문

Acetic acid can also react as a very weak base (pKb = 20). Two different sites on acetic acid might become protonated to give the conjugate acid. Draw both of these possible conjugate acids, and explain (resonance) why the correct one is more stable. Calculate the pKa of this conjugate acid.

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교과서 질문

Consider each pair of bases, and explain which one is more basic. Draw their conjugate acids, and show which one is a stronger acid.

(a)

(b)

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1
rank
교과서 질문

Give the structures of their conjugate acids, and estimate their pKas from similar compounds in Appendix 4.

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교과서 질문

Choose the more acidic member of each pair of isomers, and show why the acid you chose is more acidic.

(d)

(e)

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교과서 질문

Choose the more acidic member of each pair of isomers, and show why the acid you chose is more acidic.

(a)

(b)

(c)

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