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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Administrative data

Endpoint:
dissociation constant
Type of information:
calculation (if not (Q)SAR)
Remarks:
Migrated phrase: estimated by calculation
Adequacy of study:
other information

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1993
Report date:
1993

Materials and methods

Test material

Reference
Name:
Unnamed
Type:
Constituent

Results and discussion

Dissociation constant
No.:
#1
pKa:
ca. 1
Temp.:
25 °C
Remarks on result:
other: estimation

Any other information on results incl. tables

For benzoic acid the following pKa value is published (I. Cadariu, et al. Z. Phys. Chem. (Leipzig) 242, 391, 1969):

pKa = 4.2

The change in acid strength, produced by substituents in different positions of the benzene ring can

be predicted (D.D. Perrin, B. Dempsey, E.P. Serjeant; pKa predicition for organic acids and bases,

Chapman and Hall, 1981) using the Hammett equation (Equ.1)

                           1.               pKa = pKa° - rho(sum of sigma)

were pKa° is the acid dissociation constant of the unsubstituted acid,is the Hammett con­stant,

assigned to particular substituents andis a constant for a particular equilibrium (unity for benzoic acids).

The pKa values of the substituted acid were obtained by summing theconstants of all substituents and

substracting the total from the pKa of the parent acid as follows:

functional group

sigma value

 sum of sigma

2 Iortho

1 Ipara

(NH2)meta

m - CONHCH3

1.34

0.21

0

0.35

2.68

0.21

0

0.35

  rho(sum of sigma) = 3.24

Using Equation 1 the following pKa value of ZK 39 211 could be estimated:

pKa = 0.96

Therefore it can be expected that ZK 39 211 is present as anion in a pH range pH > 3.

Applicant's summary and conclusion

Executive summary:

From the published acid dissociation constants of benzoic acid (Ref.1) the following pKa value

of ZK 39211 was estimated using the Hammett equation (D.D. Perrin, B. Dempsey, E.P. Serjeant;

pKa predicition for organic acids and bases, Chapman and Hall, 1981):

pKa = 1.0