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Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics
Mullins - Organic Chemistry: A Learner Centered Approach 1st Edition
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Tutti i libri di testoMullins 1st EditionCh. 5 - Chemical Reaction Analysis: Thermodynamics and KineticsProblema 3a
Capitolo 4, Problema 3a

Which is the most stable base in each pair?
(a)

Guida verificata passo dopo passo
1
Step 1: Analyze the chemical structures provided in the image. The first structure is a deprotonated ketone (a carbonyl group with a negative charge on the carbon atom), while the second structure is a deprotonated carboxylic acid (a carbonyl group with a negative charge on the oxygen atom).
Step 2: Recall that the stability of a base is influenced by the ability of the molecule to delocalize or stabilize the negative charge. Resonance and electronegativity play key roles in this stabilization.
Step 3: Evaluate the resonance possibilities for each structure. In the deprotonated carboxylic acid, the negative charge on the oxygen atom can be delocalized through resonance with the adjacent carbonyl group, making it more stable. In contrast, the negative charge on the carbon atom in the deprotonated ketone has limited resonance stabilization.
Step 4: Consider electronegativity. Oxygen is more electronegative than carbon, meaning it is better able to stabilize a negative charge. This further contributes to the stability of the deprotonated carboxylic acid compared to the deprotonated ketone.
Step 5: Conclude that the deprotonated carboxylic acid (the structure with the negative charge on the oxygen atom) is the more stable base in this pair due to resonance stabilization and the electronegativity of oxygen.

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Acidity and Basicity

In organic chemistry, acidity refers to the tendency of a compound to donate a proton (H+), while basicity is the ability to accept a proton. The stability of a base is often inversely related to the acidity of its conjugate acid. Understanding the relationship between acids and bases is crucial for determining which species is more stable in a given pair.
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Understanding the difference between basicity and nucleophilicity.

Resonance Stabilization

Resonance stabilization occurs when a molecule can be represented by two or more valid Lewis structures, allowing the electron density to be delocalized. This delocalization lowers the energy of the molecule, making it more stable. In the context of the question, the presence of resonance in one of the bases can significantly influence its stability compared to the other.
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The radical stability trend.

Electronegativity and Charge Distribution

Electronegativity is the tendency of an atom to attract electrons towards itself. In the context of charged species, the stability of a base can be affected by the electronegativity of the atom bearing the charge. A more electronegative atom can better stabilize a negative charge, leading to a more stable base. This concept is essential for comparing the stability of the bases shown in the image.
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Electronegativity
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