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Ch. 4 - Acids and Bases/Electron Flow
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Non è quello che usi tu?Cambia libro di testo
Capitolo 3, Problema 63d

Identify the stronger base in each pair. Explain your choice. Citing pKa values is not an acceptable answer.
(d)

Guida verificata passo dopo passo
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Step 1: Understand the concept of basicity. Basicity refers to the ability of a species to donate a pair of electrons to a proton (H⁺). Stronger bases are more willing to donate their electrons.
Step 2: Analyze the electronegativity of the atoms involved. Fluorine (F⁻) is highly electronegative, meaning it strongly attracts electrons and is less willing to donate them, making it a weaker base.
Step 3: Consider the structure of the tert-butoxide ion (O⁻ in the tert-butyl group). Oxygen is less electronegative than fluorine, so it is more willing to donate its electrons. Additionally, the bulky tert-butyl group provides steric hindrance, which can reduce the stability of the conjugate acid formed after protonation, favoring the base form.
Step 4: Evaluate the conjugate acid stability. The conjugate acid of F⁻ (HF) is very stable due to strong hydrogen bonding, while the conjugate acid of tert-butoxide (tert-butanol) is less stable, making tert-butoxide a stronger base.
Step 5: Conclude that the tert-butoxide ion is the stronger base compared to the fluoride ion because it is less electronegative and its conjugate acid is less stable, favoring the base form.

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Acidity and Basicity

Acidity refers to the tendency of a compound to donate protons (H⁺ ions), while basicity is the tendency to accept protons. The strength of a base is often related to its ability to stabilize the negative charge after accepting a proton. Understanding the relationship between acids and bases is crucial for determining which compound in a pair is the stronger base.
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Understanding the difference between basicity and nucleophilicity.

Resonance Stabilization

Resonance stabilization occurs when a molecule can be represented by multiple valid Lewis structures, allowing for the delocalization of electrons. This delocalization can stabilize the negative charge on a base, making it a stronger base. Analyzing the resonance structures of the bases in question can help identify which one is more stable and thus a stronger base.
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The radical stability trend.

Electronegativity and Inductive Effects

Electronegativity is the tendency of an atom to attract electrons, and it plays a significant role in determining the strength of a base. Atoms or groups that are more electronegative can withdraw electron density through inductive effects, making the conjugate base less stable. Evaluating the electronegativity of atoms in the base can provide insight into its strength relative to another base in the pair.
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Electronegativity