Table 3.1 pKa Values of Common Compounds and Their Conjugate Bases

A complete set of vocabulary flashcards detailing the pKa values, acid strengths, and conjugate bases of common compounds shown in Table 3.1.

Acid Strength and $pK_a$ Relationship

The principle that acid strength increases as the $pK_a$ value decreases; in Table 3.1, the strongest acid has a $pK_a$ of $-9$ and the weakest acid has a $pK_a$ of $50$.

Conjugate Base Strength and $pK_a$ Relationship

The principle that conjugate base strength increases as the $pK_a$ of its conjugate acid increases; the weakest base corresponds to the strongest acid ($pK_a = -9$), while the strongest base corresponds to the weakest acid ($pK_a = 50$).

Sulfuric Acid ($H_2SO_4$ )

The strongest acid listed in Table 3.1 with a $pK_a$ of $-9$, forming the weakest conjugate base ($H_2SO_4$ ).

Protonated Acetone (CH3)2CO

An acid with a $pK_a$ of $-7.3$, which yields acetone as its conjugate base upon deprotonation.

Hydrochloric Acid ($Cl-H$)

A strong mineral acid with a $pK_a$ of $-7$, whose conjugate base is the chloride ion ($Cl^-$).

Hydronium Ion ($H_3O^+$)

A protonated oxygen species with a $pK_a$ of $-1.74$, which produces water ($H_2O$) as its conjugate base.

Acetic Acid

A carboxylic acid with a $pK_a$ of $4.75$, whose conjugate base is the acetate ion.

2,4-Pentanedione

A dicarbonyl compound with acidic methylene protons having a $pK_a$ of $9.0$.

Phenol

An aromatic alcohol compound with a $pK_a$ of $9.9$, whose conjugate base is the phenoxide anion.

Water ($H_2O$)

A neutral compound with a $pK_a$ of $15.7$, whose conjugate base is the hydroxide ion ($HO^-$).

Ethanol

A primary alcohol with a $pK_a$ of $16$, which forms ethoxide as its conjugate base.

tert-Butanol

A tertiary alcohol with a $pK_a$ of $18$, which forms tert-butoxide as its conjugate base.

Acetone

A ketone possessing alpha hydrogens with a $pK_a$ of $19.2$, yielding an enolate conjugate base.

Ethyne

An alkyne ($H-C \equiv C-H$) with a $pK_a$ of $25$, whose conjugate base is an acetylide anion ($H-C \equiv C^-$).

Ammonia ($NH_3$)

A compound acting as an acid with a $pK_a$ of $38$, whose conjugate base is the amide ion ($NH_2^-$).

Ethene

An alkene ($H_2C=CH_2$) with a $pK_a$ of $44$, which yields a vinyl anion as its conjugate base.

Ethane

The weakest acid listed in Table 3.1 with a $pK_a$ of $50$, whose conjugate base ($H_3C-CH_2^-$) is the strongest base listed.