Accuracy of Prediction of pKa (Home)

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By use of a new keyword -  "pKa" - the pKa of the most readily ionized hydrogen atoms attached to oxygen atoms will be printed.  The pKa calculation uses the charge on the hydrogen and the O-H bond-length, and for a set of simple organic compounds has the following accuracy:

Average signed error: -0.02
Median error 0.21
Average unsigned error:  0.31
Root mean square error:     0.43

Individual Species used in Preparing this Graph

Molecule

Exp. pKa

Calc'd pKa

Diff.

|Diff.|

(Diff.)^2

1-Naphthoic acid

3.69

4.35

0.66

0.66

0.43

2,2,2-Trichloroethanol

12.02

12.22

0.20

0.20

0.04

2,2,2-Trifluoroethanol

12.40

12.27

-0.13

0.13

0.02

2,2-Dimethylpropionic acid

5.03

5.23

0.20

0.20

0.04

2,3,4,6-Tetrachlorophenol

5.62

6.08

0.46

0.46

0.21

2,3,4-Trichlorophenol

7.10

7.17

0.07

0.07

0.00

2,3-Dichlorophenol

7.76

7.81

0.05

0.05

0.00

2,4,5-Trichlorophenol

7.07

7.02

-0.05

0.05

0.00

2,4,6-Trichlorophenol

6.21

6.30

0.09

0.09

0.01

2,4,6-Trinitrophenol

0.60

0.54

-0.06

0.06

0.00

2,4-Dichlorophenol

8.09

7.40

-0.69

0.69

0.48

2,5-Dichlorophenol

7.51

7.62

0.11

0.11

0.01

2,6-Dichlorophenol

6.79

7.03

0.24

0.24

0.06

2-Chlorobutanoic acid

2.86

2.72

-0.14

0.14

0.02

2-Chlorophenol

8.29

8.22

-0.07

0.07

0.01

2-Chloropropanoic acid

2.83

2.93

0.10

0.10

0.01

2-Hydroxypropanoic acid

3.86

3.31

-0.55

0.55

0.30

2-Naphthoic acid

4.17

4.23

0.06

0.06

0.00

3,4-Dichlorophenol

8.68

8.31

-0.37

0.37

0.13

3,5-Dichlorophenol

8.27

8.33

0.06

0.06

0.00

3-Chlorobutanoic acid

4.05

4.28

0.23

0.23

0.05

3-Chlorophenol

8.78

8.96

0.18

0.18

0.03

3-Chloropropanoic acid

3.98

4.29

0.31

0.31

0.10

4-Chlorobutanoic acid

4.53

4.71

0.18

0.18

0.03

4-Chlorophenol

9.14

8.81

-0.33

0.33

0.11

Acetic acid

4.76

5.00

0.24

0.24

0.06

Acrylic acid

4.25

4.65

0.40

0.40

0.16

Alanine

2.35

2.36

0.01

0.01

0.00

Argenine

2.35

2.34

-0.01

0.01

0.00

Ascorbic acid

4.17

2.64

-1.53

1.53

2.35

Asparagine

2.01

2.02

0.01

0.01

0.00

Aspartic acid

2.10

1.98

-0.12

0.12

0.01

Benzohydroxamic acid

8.88

8.89

0.01

0.01

0.00

Benzoic acid

4.20

4.30

0.10

0.10

0.01

Benzophenone oxime

11.30

11.18

-0.12

0.12

0.01

Bromoacetic acid

2.86

3.11

0.25

0.25

0.06

Butanoic acid

4.82

4.78

-0.04

0.04

0.00

Chloroacetic acid

2.86

4.18

1.32

1.32

1.74

Citric acid

3.13

2.56

-0.57

0.57

0.32

Cyanoacetic acid

2.43

1.74

-0.69

0.69

0.47

Cysteine

2.05

1.42

-0.63

0.63

0.40

Dichloroacetic acid

1.26

1.42

0.16

0.16

0.02

Ethanol

16.00

16.37

0.37

0.37

0.14

Fluoroacetic acid

2.66

2.96

0.30

0.30

0.09

Formic acid

3.77

3.77

0.00

0.00

0.00

Fumaric acid

3.02

3.22

0.20

0.20

0.04

Glutamic acid

2.10

2.01

-0.09

0.09

0.01

Glutamine

2.17

2.49

0.32

0.32

0.10

Glycine

2.35

2.53

0.18

0.18

0.03

Histidine

1.77

1.98

0.21

0.21

0.04

Iodoacetic acid

3.12

3.30

0.18

0.18

0.03

Isoleucine

2.32

2.48

0.16

0.16

0.02

Isophthalic acid

3.46

3.50

0.04

0.04

0.00

Leucine

2.33

2.38

0.05

0.05

0.00

Lysine

2.18

2.53

0.35

0.35

0.12

m-Chlorobenzoic acid

3.82

3.80

-0.02

0.02

0.00

m-Chlorophenol

9.02

8.99

-0.03

0.03

0.00

m-Cresol

10.08

9.63

-0.45

0.45

0.21

m-Hydoxybenzoic acid

4.08

4.03

-0.05

0.05

0.00

m-Hydroxyaniline

9.87

9.11

-0.76

0.76

0.58

m-Hydroxybenzaldehyde

8.00

9.34

1.34

1.34

1.80

m-Methoxybenzoic acid

4.09

4.07

-0.02

0.02

0.00

m-Methoxyphenol

9.66

9.06

-0.60

0.60

0.36

m-Methylbenzoic acid

4.27

4.41

0.14

0.14

0.02

m-Methylphenol

10.08

9.77

-0.31

0.31

0.10

m-Nitrobenzoic acid

3.49

3.19

-0.30

0.30

0.09

m-Nitrophenol

8.39

7.75

-0.64

0.64

0.41

Malaic acid

1.93

1.81

-0.12

0.12

0.01

Methanol

15.54

15.23

-0.32

0.32

0.10

Methionine

2.28

2.30

0.02

0.02

0.00

n-Pentanoic acid

4.82

4.77

-0.06

0.06

0.00

o-Cresol

10.28

11.17

0.89

0.89

0.80

o-Hydroxyaniline

9.71

9.08

-0.63

0.63

0.39

o-Hydroxybenzaldehyde

6.79

7.54

0.75

0.75

0.57

o-Nitrophenol

7.17

7.52

0.35

0.35

0.12

Oxalic acid

1.23

1.60

0.37

0.37

0.13

p-Aminophenol

10.46

9.85

-0.61

0.61

0.37

p-bromobenzoic acid

4.00

3.61

-0.39

0.39

0.15

p-Bromophenol

9.35

8.72

-0.63

0.63

0.40

p-Chlorobenzoic acid

3.99

3.99

0.00

0.00

0.00

p-Chlorophenol

9.38

8.82

-0.56

0.56

0.31

p-Cresol

10.19

10.27

0.08

0.08

0.01

p-Hydoxybenzoic acid

4.59

4.63

0.04

0.04

0.00

p-Hydroxyaniline

10.30

10.41

0.11

0.11

0.01

p-Hydroxybenzaldehyde

7.66

8.09

0.43

0.43

0.18

p-Iodophenol

9.30

8.67

-0.63

0.63

0.40

p-Methoxybenzoic acid

4.48

4.82

0.34

0.34

0.11

p-Methoxyphenol

10.21

10.63

0.42

0.42

0.17

p-Methylbenzoic acid

4.38

4.66

0.28

0.28

0.08

p-Methylphenol

10.17

10.29

0.12

0.12

0.01

p-Nitrobenzoic acid

3.49

2.95

-0.55

0.55

0.30

p-Nitrophenol

7.15

7.29

0.14

0.14

0.02

Pentachlorophenol

4.90

5.55

0.65

0.65

0.42

Phenol

10.00

9.71

-0.29

0.29

0.09

Phenylalanine

2.58

2.01

-0.57

0.57

0.33

Phthalic acid

2.98

2.40

-0.58

0.58

0.33

Proline

2.00

2.36

0.36

0.36

0.13

Propionic acid

4.88

4.91

0.03

0.03

0.00

Pyruvic acid

2.50

2.85

0.35

0.35

0.12

Serine

2.21

1.86

-0.35

0.35

0.12

t-Butanol

17.00

16.25

-0.75

0.75

0.56

Terephthalic acid

3.51

3.59

0.08

0.08

0.01

Threonine

2.09

1.95

-0.14

0.14

0.02

Trichloroacetic acid

0.63

-0.40

-1.03

1.03

1.06

Trifluoroacetic acid

0.00

-0.18

-0.18

0.18

0.03

Tryptophan

2.38

2.39

0.01

0.01

0.00

Tyrosine

2.20

2.43

0.23

0.23

0.05

Valine

2.29

2.61

0.32

0.32

0.10

Water

15.74

15.75

0.01

0.01

0.00