For the bases shown, draw the conjugate acid and identify a pK_a value from Table 4.5 that would help you accurately estimate its stability.
(c)

검증된 단계별 안내

Step 1: Identify the base in the given structure. The base shown is an alkoxide ion, specifically a phenyl isopropyl alkoxide (C₆H₅-CH(CH₃)₂-O⁻). The negatively charged oxygen atom indicates that this is a base.

Step 2: Draw the conjugate acid of the base. To form the conjugate acid, add a proton (H⁺) to the negatively charged oxygen atom. This results in the structure C₆H₅-CH(CH₃)₂-OH, which is an alcohol.

Step 3: Recall the relationship between conjugate acids and bases. The conjugate acid is less basic and more stable than the base due to the addition of a proton, which neutralizes the negative charge.

Step 4: Use Table 4.5 to identify the pKₐ value of the conjugate acid. Alcohols typically have pKₐ values around 16-18, depending on the specific structure. The stability of the conjugate acid can be estimated using this pKₐ value.

Step 5: Analyze the stability of the conjugate acid. The phenyl group and isopropyl group may contribute to steric hindrance and electronic effects, which can slightly influence the pKₐ value and stability. Compare this to other alcohols in Table 4.5 for a more accurate estimation.

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주요 개념

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

Conjugate Acids and Bases

In acid-base chemistry, a conjugate acid is formed when a base accepts a proton (H⁺). Understanding this concept is crucial for predicting the behavior of substances in reactions. For example, when ammonia (NH₃) acts as a base, it can accept a proton to form ammonium (NH₄⁺), its conjugate acid.

pKₐ and Acid Strength

pKₐ is a quantitative measure of the strength of an acid in solution; it is the negative logarithm of the acid dissociation constant (Kₐ). A lower pKₐ value indicates a stronger acid, which dissociates more completely in solution. This concept is essential for comparing the stability of conjugate acids formed from different bases.

Stability of Conjugate Acids

The stability of a conjugate acid is influenced by factors such as electronegativity, resonance, and inductive effects. A more stable conjugate acid corresponds to a stronger base, as it is less likely to donate a proton. Evaluating stability helps in predicting the direction of acid-base reactions and the relative strengths of acids and bases.

For the bases shown, draw the conjugate acid and identify a pKa value from Table 4.5 that would help you accurately estimate its stability.(c)