Organic Chemistry pKa Table and Functional Groups

Flashcards covering key functional groups, chemical structures, and pKa values from organic chemistry reference notes.

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Sulfuric Acid ($\text{H}_2\text{SO}_4$). pKa​: −9 IR Range: N/A

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p-Toluenesulfonic Acid / Tosic Acid ($\text{TsOH}$) . pKa​: −7 IR Range: Aromatic ∼1600 cm−1, ∼1500 cm−1

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Hydrogen Halides ($\text{HX}$). $\text{p}K_a$ values of $-7$, $-9$, and $-10$

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Hydronium Ion ($\text{H}_3\text{O}^+$) pKa​: −1.7

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Protonated Alcohol or Ether ($\text{ROH}_2^+$ or $\text{R}_2\text{OH}^+$). $\text{p}K_a = -2$.

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Nitric Acid ($\text{HNO}_3$) $\text{p}K_a = -1.3$.

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Carboxylic Acid ($\text{RCO}_2\text{H}$). typical $\text{p}K_a = 4 - 5$. IR: 2400-3000 cm^-1 broad and irregular

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Ammonium Ion ($\text{HNR}_3^+$), with a typical $\text{p}K_a = 9 - 10$.

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Thiol ($\text{RSH}$), with a typical $\text{p}K_a = 10$

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Amide ($\text{RCONH}_2$)$\text{p}K_a = 15 - 17$. IR: 3200-3500 (broad, sometimes irregular)

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Alcohol ($\text{ROH}$), with a typical $\text{p}K_a = 16 - 18$. IR: 3200-3600 Broad, Symmetrical

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Aldehyde ($\text{RCHO}$) ; the $\alpha$-hydrogen ($\text{H}_A$) has a $\text{p}K_a = 17$, while the carbonyl hydrogen ($\text{H}_B$) has a $\text{p}K_a = 50$. IR: 1720-1725

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Ketone ($\text{RCOR}$) $\alpha$-hydrogen has a typical $\text{p}K_a = 20$. IR: 1710-1715

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Ester ($\text{R'CO}_2\text{R}$); the $\alpha$-hydrogen ($\text{H}_A$) has a $\text{p}K_a = 25$, and the alkoxy proton ($\text{H}_B$) has a $\text{p}K_a = 50$. IR: 1735-1745

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Alkyne ($\text{RCCH}$) , having a $\text{p}K_a = 25$. IR: sp is 3300, or 2100-2300

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Amine ($\text{HNR}_2$) , with an $\text{N-H}$ $\text{p}K_a = 38$. IR: 3200-3500 (broad, sometimes irregular)

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Benzylic Hydrogen ($\text{PhCH}_3$), having a $\text{p}K_a = 41$. IR: Aromatic - 1500-1600

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Allylic Hydrogen , with a $\text{p}K_a = 43$. IR: sp2 - 3050, otherwise 1640-1670

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Aromatic Ring ($\text{PhH}$), with a $\text{p}K_a = 43$. IR: 1500-1600

Alkene ($\text{R}_2\text{CCHR}$), $\text{p}K_a = 44$. IR: sp2 - 3050, otherwise 1640-1670

Alkane ($\text{R}_3\text{CH}$),$\text{p}K_a = 50$. IR: sp3 - 2900, otherwise in the fingerprint region 1500 and below

Ether ($\text{ROR}$),$\text{p}K_a = 50$ . IR: 3200 ish

Alkyl Halide ($\text{RX}$ or $\text{H}_3\text{C-X}$) $\text{p}K_a \approx 50$.

Epoxide $\text{p}K_a \approx 50$.