题目

CHE 008B A01 SS1 2025 Lecture 8 - Enolate Ions

多重下拉选择题

For each pair determine which is the better acid (lower pKa) at the alpha hydrogen. Pair 1: [ Select ] CH3COCH2COCH3 - 2,4-pentanedione CH3COCH2CH2CH3 - 2-pentanone they're the same cannot tell Pair 2: [ Select ] CH3COCH2CH2CH3 - 2-pentanone CH3CH2CH2CH2CH2CHO - pentanal they're the same cannot tell Pair 3: [ Select ] CH3OCOCH2COOCH3 dimethyl malonate (beta-diester) CH3COCH2COCH3 - 2,4-pentanedione they are the same cannot tell

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标准答案

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思路分析

We start by restating each pair and the options involved to ground the analysis before evaluating. Pair 1: Options for which compound is the better acid at the alpha hydrogen are: - CH3COCH2COCH3 - 2,4-pentanedione - CH3COCH2CH2CH3 - 2-pentanone - they're the same - cannot tell To compare acidity, we consider how easily the alpha hydrogen can be removed to form a resonance-stabilized enolate. A 1,3-dicarbonyl system (two carbonyls separated by a carbon) provides strong stabilization of the enolate due to resonance with both carbonyl groups. In 2,4-pentanedione (acetylacetone), deprotonation......Login to view full explanation