L-2-hydroxy-2-phenylacetic acid

Dissociation constant

Administrative data

Endpoint:

dissociation constant

Type of information:

calculation (if not (Q)SAR)

Remarks:

Migrated phrase: estimated by calculation

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Scientifically accepted calculation method.

Data source

Reference

Reference 1

Reference Type:

publication

Title:

Estimation of Chemical Reactivity Parameters and Physical Properties of Organic Molecules Using SPARC (Book Chapter)

Author:

L. A. Carreira, S. Hilal and S. W. Karickhoff

Year:

1994

Bibliographic source:

Theoretical and Computational Chemistry, Quantitative Treatment of Solute/Solvent Interactions, Eds. P. Politzer and J. S. Murray, Elsevier Publishers

Reference 2

Reference Type:

publication

Title:

A Rigorous Test for SPARC's Chemical Reactivity Models: Estimation of more than 4300 Ionization pKa's

Author:

S. Hilal, S. W. Karickhoff and L. A. Carreira

Year:

1995

Bibliographic source:

Quant. Struc. Act. Rel., 14, 348

Materials and methods

Principles of method if other than guideline:

Calculation of pKa with SPARC, July 2007 release v3.1

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

L-2-hydroxy-2-phenylacetic acid

EC Number:

210-276-6

EC Name:

L-2-hydroxy-2-phenylacetic acid

Cas Number:

611-71-2

Molecular formula:

C8H8O3

IUPAC Name:

hydroxy(phenyl)acetic acid

Constituent 2

Reference substance name:

O=C(O)C(O)c(cccc l)c I

IUPAC Name:

O=C(O)C(O)c(cccc l)c I

Details on test material:

Name of test material (as cited in study report): (R)-(-)-α-hydroxybenzeneacetic acid
Analytical purity: pure

Results and discussion

Dissociating properties:

yes

Dissociation constant

No.:

#1

pKa:

3.66

Temp.:

25 °C

Remarks on result:

other: Further details on the result can be found under "Any other information on results incl. tables"

Any other information on results incl. tables

SPARC has estimated 1 species for the present compound. Under environmental conditions (pH 4 to 9) the distribution of the single species is as follows.

	Amount of species [%]
	pH 4	pH 7	pH 9	SMILES
Species 1	0.32	0.00	0.00	O=C(O)C(O)c(cccc1)c1
Species 2	0.68	1.00	1.00	O=C([O-1])C(O)c(cccc1)c1

Two different molecular species of the substance will occur
(shown as SMILES codes):

1 O=C(O)C(O)c(cccc1)c1      (uncharged molecule)
2 O=C([O-1])C(O)c(cccc1)c1  (charged molecule)

Depending on pH, the substance will exist to following parts
as species 1 and 2:
pH             Species 1     Species 2
-0.20          1.00          0.00
0.00          1.00          0.00
0.20          1.00          0.00
0.40          1.00          0.00
0.60          1.00          0.00
0.80          1.00          0.00
1.00          1.00          0.00
1.20          1.00          0.00
1.40          0.99          0.01
1.60          0.99          0.01
1.80          0.99          0.01
2.00          0.98          0.02
2.20          0.97          0.03
2.40          0.95          0.05
2.60          0.92          0.08
2.80          0.88          0.12
3.00          0.82          0.18
3.20          0.74          0.26
3.40          0.65          0.35
3.60          0.54          0.46
3.80          0.42          0.58
4.00          0.32          0.68
4.20          0.23          0.77
4.40          0.16          0.84
4.60          0.10          0.90
4.80          0.07          0.93
5.00          0.04          0.96
5.20          0.03          0.97
5.40          0.02          0.98
5.60          0.01          0.99
5.80          0.01          0.99
6.00          0.00          1.00
6.20          0.00          1.00
6.40          0.00          1.00
...           ...           ...
13.60          0.00          1.00
13.80          0.00          1.00
14.00          0.00          1.00

The pKa of the substance (3.66) indicates that except in
environments with low pH (e.g. pH < 3.5), the
substance will exist predominantly in the protonated form.