1. a. (i) Identify the alpha-hydrogens in compounds A and B shown below. Provide approximate $\mathrm{pK}_{\mathrm{a}}$ values for these hydrogens. Account for your answers using resonance structures.
A
B
[8 marks]

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∻Solution∻ ‖ 1 ⋮ **Identify alpha-hydrogens in compound A**: Alpha-hydrogens are those attached to the carbon adjacent to a carbonyl group. In compound A, there is one alpha carbon with one hydrogen attached to it. ‖ ‖ 2 ⋮ **Approximate $\mathrm{pK}_\mathrm{a}$ value for alpha-hydrogens in compound A**: The $\mathrm{pK}_\mathrm{a}$ of an alpha-hydrogen in a simple carbonyl compound like compound A is typically around 20. ‖ ‖ 3 ⋮ **Identify alpha-hydrogens in compound B**: Compound B has two aromatic rings connected by a carbonyl group. The alpha-hydrogens are those on the carbons adjacent to the carbonyl group. There may be multiple alpha-hydrogens due to the presence of multiple alpha carbons. ‖ ‖ 4 ⋮ **Approximate $\mathrm{pK}_\mathrm{a}$ value for alpha-hydrogens in compound B**: The $\mathrm{pK}_\mathrm{a}$ values for alpha-hydrogens in compound B are influenced by the resonance stabilization provided by the aromatic rings. These values are typically higher than those of simple carbonyl compounds, often in the range of 20-25. ‖ ‖ 5 ⋮ **Account for answers using resonance structures**: Resonance structures can delocalize the negative charge after deprotonation of the alpha-hydrogen, stabilizing the resulting enolate ion. This stabilization is greater in compound B due to the aromatic rings, which can contribute to the resonance stabilization. ‖ ∻Answer∻ ⚹ Compound A has one alpha-hydrogen with a $\mathrm{pK}_\mathrm{a}$ of approximately 20. Compound B has multiple alpha-hydrogens with $\mathrm{pK}_\mathrm{a}$ values typically in the range of 20-25, influenced by resonance stabilization from the aromatic rings. ⚹ ∻Key Concept∻ ⚹ Alpha-hydrogens are located on the carbon adjacent to a carbonyl group, and their $\mathrm{pK}_\mathrm{a}$ values are influenced by the ability of the molecule to stabilize the negative charge through resonance. ⚹ ∻Explanation∻ ⚹ The $\mathrm{pK}_\mathrm{a}$ values of alpha-hydrogens are approximated based on the stability of the conjugate base formed after deprotonation. Resonance structures that delocalize the negative charge increase this stability, leading to higher $\mathrm{pK}_\mathrm{a}$ values. ⚹◊What are the potential resonance structures that can affect the pKa values of the alpha-hydrogens in compounds A and B?⍭ Generate me a similar question◊

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