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EC number: 291-454-0
CAS number: 90411-76-0
1. Defined endpoint: Dissociation constant (pKa) in water
2. Unambiguous algorithm: For the side chain of the substance the
following fragment descriptors (parent compound) were identified as
side chain: The fragment has been found in the Internal Reaction Centers
Database. The structure used for calculation of pKa fully covered
3. Applicable domain: The identified reaction center has been
found as fragments in the Internal Reaction Centers Database with
estimated equation. The side chain calculated contains only 16 atoms,
which is much less than the limit of ACD/pKa DB of 255. The
substance/side chain only contains one ionization centre with one
fragment. The substance does not contain the atoms, which are not
accepted by ACD/pKa DB. The fragment that occur in the structure of the
side chains applied by the program are verified by the user. The rules
applied for the substance/side chain appear appropriate. An individual
uncertainty for the investigated substance is not available.
4. Statistical characteristics: Each calculation from ACD/pKa DB
is provided with its 95 % confidence interval and, if available,
literature references with experimental results. The accuracy of
calculations for simple structures is usually better than ±0.2 pKa units
(for complex structures it is better than ±0.5 pKa units).
5. Mechanistic interpretation: The mechanistic basis of the model
is the linear free energy relationship (LFER), which is an empirical
correlation between the standard free energies of reaction or activation
for two series of reactions, both subjected to the same variations in
reactant structures or reaction conditions. As applied to the estimation
of acid dissociation constants, the LFER is basically a
6. Adequacy of prediction: The result for the side chains and as
a conclusion also for the entire molecule fall within the applicability
domain described above and the estimation rules applied for the
substance appear appropriate. Therefore the predicted value can be
considered reliable yielding a useful result for further assessment.
The dissociation constant for the substance was estimated via an
external side chain (sulfonic acid) which was used for calculation as
the entire molecule of the substance was too large for the calculation
and is further not assumed to be present in its undissociated form as no
ionization centers are available. This chain is assumed to be the only
dissociable region within the molecule and as a conclusion could be used
to represent the dissociation behaviour of the entire molecule.
The following dissociation constant was estimated for the side chain:
Side chain (sulfonic acid):
pKa (HL/H+L) = -0.60 ± 0.50
The dissociation constant of the substance was estimated by ACD/pKa DB
included in ACD/labs 7.00 Release. According to the estimated results,
the side chain (sulfonic acid) is mainly present in the
deprotonated/dissociated form under environmentally relevant pH 5 - 9.
The dissociation constant for the substance was estimated via an external side chain (sulfonic acid) which was used for calculation as the entire molecule of the substance was too large for the calculation. This chain is assumed to be the only dissociable region within the molecule and as a conclusion could be used to represent the dissociation behaviour of the entire molecule.The following dissociation constant was estimated for the side chain:Side chain (sulfonic acid): pKa (HL/H+L) = -0.60 ± 0.50
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