Question

Order the following molecules on the basis of their nucleophilic strength using the pKₐ values of their conjugate acids.

Accepted Answer

Step 1: Understand the relationship between nucleophilicity and the pKₐ values of the conjugate acids. Nucleophilicity is influenced by the basicity of the molecule, which can be inferred from the pKₐ of its conjugate acid. A higher pKₐ value indicates a weaker conjugate acid and a stronger base, which typically corresponds to higher nucleophilicity. Step 2: Identify the conjugate acids of the given molecules. For ethanol (CH₃CH₂OH), the conjugate acid is ethanol itself. For ethoxide (CH₃CH₂O⁻), the conjugate acid is ethanol (CH₃CH₂OH). For ethylamine (CH₃CH₂NH₂), the conjugate acid is ethylammonium ion (CH₃CH₂NH₃⁺). For acetate ion (CH₃COO⁻), the conjugate acid is acetic acid (CH₃COOH). Step 3: Research or recall the approximate pKₐ values of the conjugate acids: Ethanol has a pKₐ of around 16, ethylammonium ion has a pKₐ of around 10.6, and acetic acid has a pKₐ of around 4.8. Ethoxide is the conjugate base of ethanol, so its nucleophilicity is related to ethanol's pKₐ. Step 4: Compare the pKₐ values to determine nucleophilic strength. Molecules with higher pKₐ values of their conjugate acids are stronger nucleophiles. Based on the pKₐ values: Ethoxide (CH₃CH₂O⁻) \u003e Ethylamine (CH₃CH₂NH₂) \u003e Acetate ion (CH₃COO⁻). Ethanol (CH₃CH₂OH) is neutral and less nucleophilic compared to the charged species. Step 5: Order the molecules based on nucleophilic strength: Ethoxide (CH₃CH₂O⁻) is the strongest nucleophile, followed by ethylamine (CH₃CH₂NH₂), then acetate ion (CH₃COO⁻), and finally ethanol (CH₃CH₂OH) as the weakest nucleophile.

Order the following molecules on the basis of their nucleophilic strength using the pKₐ values of their conjugate acids.

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Concetti chiave

Nucleophilicity

pKₐ and Conjugate Acids

Order of Nucleophiles