The p Ka of acetone, C H3 C O C H3, is 19.3 . Which of the...

The $p K_{a}$ of acetone, $C H_{3} C O C H_{3}$, is $19.3 .$ Which of the following bases is strong enough to deprotonate acetone? (a) $\mathrm{KOH}\left(\mathrm{pK}_{2} \text { of } \mathrm{H}_{2} \mathrm{O}=15.7\right)$ (b) $\mathrm{Na}^{+}-\mathrm{C}=\mathrm{CH}\left(\mathrm{p} K_{\mathrm{a}} \text { of } \mathrm{C}_{2} \mathrm{H}_{2}=25\right)$ (c) $\mathrm{NaHCO}_{3}\left(\mathrm{p} K_{\mathrm{a}} \text { of } \mathrm{H}_{2} \mathrm{CO}_{3}=6.4\right)$ (d) $\mathrm{NaOCH}_{3}\left(\mathrm{pK}_{\mathrm{a}} \text { of } \mathrm{CH}_{3} \mathrm{OH}=15.6\right)$

The $p K_{a}$ of acetone, $C H_{3} C O C H_{3}$, is $19.3 .$ Which of the following bases is strong enough to deprotonate acetone?
(a) $\mathrm{KOH}\left(\mathrm{pK}_{2} \text { of } \mathrm{H}_{2} \mathrm{O}=15.7\right)$
(b) $\mathrm{Na}^{+}-\mathrm{C}=\mathrm{CH}\left(\mathrm{p} K_{\mathrm{a}} \text { of } \mathrm{C}_{2} \mathrm{H}_{2}=25\right)$
(c) $\mathrm{NaHCO}_{3}\left(\mathrm{p} K_{\mathrm{a}} \text { of } \mathrm{H}_{2} \mathrm{CO}_{3}=6.4\right)$
(d) $\mathrm{NaOCH}_{3}\left(\mathrm{pK}_{\mathrm{a}} \text { of } \mathrm{CH}_{3} \mathrm{OH}=15.6\right)$

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Key Concepts

pKa and Acid Strength

The pKa value is a measure of the strength of an acid: a lower pKa indicates a stronger acid while a higher pKa signifies a weaker acid. This concept is crucial for predicting acid-base reactions because, in such reactions, the relative pKa values of the acid and the conjugate acid of the base determine the direction of the equilibrium. A base will successfully deprotonate an acid if the conjugate acid of the base has a higher pKa (i.e., is a weaker acid) compared to the original acid.

Conjugate Acid-Base Relationships

In acid-base chemistry, every acid has a conjugate base, and every base has a conjugate acid formed upon proton transfer. The strength of a base is typically assessed by the pKa of its conjugate acid. When the conjugate acid of a base has a significantly higher pKa than the acid being deprotonated, the deprotonation reaction is thermodynamically favored.

Acid-Base Equilibrium

Acid-base reactions are equilibrium processes that depend on the relative stabilities of the acids and bases involved. The equilibrium will favor the formation of the weaker acid and base. This principle is used to predict whether a given base is strong enough to deprotonate a particular acid by comparing the pKa values of the involved species.

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