pKa Values by Functional Group w/ Pictures

Acid Halide (HI)

-9 (Acid Halide)

Acid halide (HBr)

-8

Acid halide (HCl)

-7 (Acid Halide)

Sulfuric acid

-9

Protonated ketone

-7

Protonated alcohol

-2

Carboxylic acid

5

Protonated amine

10

Thiol

13

Alcohol/Water

16

Ketone (alpha hydrogen)

19

Amide

20

Alkyne

25 (sp)

Ester

25

Hydrogen (H₂)

36

Amine

38

Alkene

44

Alkane

50

Acid halide (HF)

4

Imine

7

Phenol

9.9

Diketone

9

Cyclopentadiene

16 (Ring)

Allylic hydrogen

43 (low 40s) (resonance)

Hydrogen Cyanide (HCN)

10 (HCN)

Cysteine

8.18

Aspartic acid

3.65

Glutamic acid

4.25

Arginine (the N that is double-bonded in the functional group is protonated)

12.48

Histidine (the double-bonded N in the functional group is protonated)

6.00

Lysine (amine in functional group is protonated)

10.50

Carboxylic acid in an amino acid

2

Amine group in an amino acid (it is protonated)

9