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Diss Factsheets
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EC number: 204-800-2 | CAS number: 126-73-8
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
Dissociation constant
Administrative data
- Endpoint:
- dissociation constant
- Type of information:
- (Q)SAR
- Adequacy of study:
- key study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
- Justification for type of information:
- 1. SOFTWARE
The dissociation constant (pKa), predicted using ACD/Percepta 14.0.0 (Build 2254).
2. MODEL (incl. version number)
ACD/pKa DB included in ACD/Percepta 14.0.0 (Build 2254, 16. Jul. 2013)
3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
The typical structure formula was imported through ChemSketch included in ACD/Percepta 14.0.0 (Build 2254).
4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
a. Defined endpoint: Dissociation constant (pKa) in water
b. Explicit algorithm: The algorithm of ACD/pKa DB ia a type of linear free energy relationship (LFER). LFER is an empirical correlation between the standard free energies of reaction or activation for two series of reactions, both subjected to the same variation in reactant structures or reaction conditions. ACD/pKa DB utilizes the Hammett relationship for aromatic systems and the Taft relationship for aliphatic substances to estimate acid dissociation constant.
The algorithm of ACD/pKa DB is built upon extensive compilation of Hammett and Taft correlations empirically derived from studying ionization equilibriums in over 15,000 compounds. The properties of this approach give it excellent reliability within the space of well characterized chemical substances. In addition, two reference databases are available that offer quick look-up of published data – one contains > 31,000 experimental pKa values for approximately 16,000 compounds in aqueous solutions; the other provides experimental data for more than 2000 molecules in non-aqueous solvents.
c. Applicability domain: Due to the fragment-based approach of ACD/pKa DB, it is adequate when the fragments present in the molecule under study are present in the database. In addition there are two techniques to improve the pka calculation when the fragments are not available, i.e. system training and accuracy extender.
d. Statistics for goodness-of-fit: Each calculation from ACD/pKa DB is provided with its 95 % confidence interval and, when available, literature references with experimental results. The accuracy of calculations for simple structures is usually better than ± 0.2 pka units (for complex structrues it is better than ± 0.5 pKa units).
e. Predictivity – statistics obtained by external validation: The accuracy statistics for the three external validation sets are reported in the literature as following: Dataset 1: correlation coeff. (r^2) = 0.9823, dataset 2: correlation coeff. (r^2) = 0.9928, dataset 3: correlation coeff. (r^2) = 0.9902.
f. Limits of applicability: The ACD/algorithm will refuse to predict pKa values for structures which:
-contain more than 225 atoms (note that the program refuses to predict pKa values for some cyclic compounds having less than 255 atoms due to the fact that the program uses cyclic-breaking algorithm that increases the number of atoms)
-do not contain an ionization center
-contain atoms of non-typical valence
-contain atoms other than C, H, O, S, P, N, F, Cl, Br, I, Se, Si, Ge, Pb, Sn, As, B
-contain two or more fragments in one ionization center
-contain more than 20 ionization center
-contain d-block or f-block metal atoms
-contain textual abbreviations which cannot be transformed to structural fragments
5. APPLICABILITY DOMAIN
a. Domains:
i. Molecular weight: Not relevant.
ii. Structural fragment domain:
- The identified reaction centres have been found as fragments in the Internal Reaction Centres Database with experimental equations.
- The substance only contains 44 atoms, which is much less than the limit of ACD/pKa DB of 255.
- The substance contains no ionization centres.
- The substance does not contain atoms, which are not accepted by ACD/pKa DB.
iii. Mechanism domain: No information available
iv. Metabolic domain, if relevant: Not relevant
b. Structural analogues: No information available
i. Considerations on structural analogues: No information available
c. The uncertainty of the prediction (OECD principle 4): The Substance is not highly complex and the rules applied for the substance appear appropriate. An individual uncertainty for the investigated substance is not available.
d. The chemical and biological mechanisms according to the model underpinning the predicted result (OECD principle 5): No information available.
6. ADEQUACY OF THE RESULT
a. Regulatory purpose: The data may be used under any regulatory purpose.
b. Approach for regulatory interpretation of the model result: If no experimental data are available, the estimated value may be used to fill data gaps needed for hazard and risk assessment.
c. Outcome: The prediction of dissociation constant (pKa) yields a useful result for further evaluation.
d. Conclusion: The result is considered as useful for regulatory purposes.
Data source
Reference
- Reference Type:
- study report
- Title:
- Unnamed
- Year:
- 2 021
- Report date:
- 2021
Materials and methods
Test guideline
- Guideline:
- other: REACH guidance on QSARs R.6, May 2008
- Principles of method if other than guideline:
- ACD 14.0.0 software program for estimating the dissociation constant (pKa) in water.The recommended method, “apparent constants, approximated”, was used for the estimation. The program was developed by Advanced Chemistry Development Inc.
90 Adelaide Street West, Toronto, Ontario, M5H 3V9, Canada (http://www.acdlabs.com); Copyright © 1997-2013; Build 2254, 16. Jul 2013 - GLP compliance:
- no
Test material
- Reference substance name:
- Tributyl phosphate
- EC Number:
- 204-800-2
- EC Name:
- Tributyl phosphate
- Cas Number:
- 126-73-8
- Molecular formula:
- C12H27O4P
- IUPAC Name:
- tributyl phosphate
Constituent 1
Results and discussion
- Dissociating properties:
- yes
Dissociation constantopen allclose all
- No.:
- #1
- Temp.:
- 25 °C
- Remarks on result:
- other: No acid pKa
- No.:
- #2
- Temp.:
- 25 °C
- Remarks on result:
- other: No base pKa
Any other information on results incl. tables
1. Defined endpoint: Dissociation constant (pKa) in water
2. Unambiguous algorithm: For tributyl phosphate, the following fragment (parent compound) descriptors were identified as reaction centres: None available
3. Applicable domain: The identified reaction centers have been found as fragments in the Internal Reaction Centers Database with experimental equations. The substance only contains 44 atoms, which is much less than the limit of ACD/pKa DB of 255. The substance contains no ionization centres. The substance does not contain any atoms, which are not accepted by ACD/pKa DB. No fragment was identified as reaction centre in the structure of tributyl phosphate by the program. The rules applied for the substance appears 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, when 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 substituent-effect approach.
6. Adequacy of prediction: The result for tributyl phosphate falls within the applicability domain described above and the estimation rules applied for the substance appears appropriate. Therefore the predicted value can be considered reliable yielding a useful result for further assessment.
Applicant's summary and conclusion
- Conclusions:
- No acid and no base pKa was predicted for tributyl phosphate.
- Executive summary:
The dissociation constant (pKa) of tributyl phosphate was predicted using ACD/Percepta 14.0.0 (Build 2254). The pKa at 25 °C is:
1. No acid pKa
2. No base pKaThe QSAR calculation supports the waiving argumentation that tributyl phosphate lacks the relevant functional groups required for dissociation.
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