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EC number: 202-653-9 | CAS number: 98-29-3
- 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
Link to relevant study record(s)
- Endpoint:
- dissociation constant
- Type of information:
- experimental study
- Adequacy of study:
- key study
- Study period:
- 1976
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- study well documented, meets generally accepted scientific principles, acceptable for assessment
- Qualifier:
- no guideline followed
- Principles of method if other than guideline:
- lonisation constants of catechin, robinetinidol, leuco-fisetinidin, fustin, dihydrorobinctin, dihydroquercetin and a series of polyphenols including the 4-ter-pyrocatechol are reported.
- GLP compliance:
- not specified
- Specific details on test material used for the study:
- The phenols tested are commercially available and were purified by either vacuum distillation or recrystallisation
- Dissociating properties:
- yes
- No.:
- #1
- pKa:
- 9.53
- Temp.:
- 20 °C
- Remarks on result:
- other: pKa1 (hydroxyl in position 2)
- No.:
- #2
- pKa:
- 14
- Temp.:
- 20 °C
- Remarks on result:
- other: pKa2 (hydroxyl in position 1)
- Conclusions:
- For the 4-ter-butylpyrocatechol, the pKa1 and the pKa2 were determined as 9.53 and 14.0 respectively.
- Executive summary:
In this study, the ionisation constants of catechin, robinetinidol, leuco-fisetinidin, fustin, dihydrorobinctin, dihydroquercetin and a series of polyphenols including the 4-ter-butylpyrocatechol were investigated.
The pKa values of these flavonoids are shown to fit the linear relationships between pKa and substituent a constant for a series of related phenols.
For the 4-ter-butylpyrocatechol (substance of interest) the pKa1 and the pKa2 were determined as 9.53 (for hydroxyl in position 2) and 14.0 (for hydroxyl in position 1) respectively.
- Endpoint:
- dissociation constant
- Type of information:
- (Q)SAR
- Adequacy of study:
- supporting study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: Model usually accepted for estimation of pKa values.
- Justification for type of information:
- 1. SOFTWARE
SPARC
2. MODEL
version available in 2010
3. SMILES OR OTHER IDENTIFIERS USED AS INPUT FOR THE MODEL
CC(C)(C)c1ccc(O)c(O)c1
4. SCIENTIFIC VALIDITY OF THE (Q)SAR MODEL
- Defined endpoint: yes, 1.10 Dissociation constant
- Unambiguous algorithm: not available for this commercial QSAR
- Defined domain of applicability: not available for this commercial QSAR
- Appropriate measures of goodness-of-fit and robustness and predictivity: Not available for this commercial QSAR
- Mechanistic interpretation:
5. APPLICABILITY DOMAIN
- Descriptor domain: not available for this commercial QSAR
- Structural and mechanistic domains: not available for this commercial QSAR
- Similarity with analogues in the training set: not available for this commercial QSAR
6. ADEQUACY OF THE RESULT - Principles of method if other than guideline:
- SPARC was developed by Karickhoff (Karickhoff et al., 1991). It estimates the following physico-chemical properties by means of linear free energy relationships and molecular orbital properties: boiling point, density, vapour pressure, water solubility, octanol/water partition coefficient, Henry’s law constant, acid dissociation constant.
Major reference:Hilal, Said, S. W. Karickhoff and L. A. Carreira,
"A Rigorous Test for SPARC's Chemical Reactivity Models: Estimation of More Than 4300 Ionization pKa's," Quant. Struc. Act. Rel., 14, 348 1995. - GLP compliance:
- no
- Dissociating properties:
- yes
- No.:
- #1
- pKa:
- 9.54
- Temp.:
- 25 °C
- Remarks on result:
- other: The reaction linked to this pKa is illustred in the attached document.
- No.:
- #2
- pKa:
- 9.73
- Temp.:
- 25 °C
- Remarks on result:
- other: The reaction linked to this pKa is illustred in the attached document.
- Conclusions:
- The pKa values for 4-TBC have been calculated by the SPARC model to be 9.53 (for hydroxyl in position 2) and 9.73 (for hydroxyl in position 1), at a temperature of 25°C.
Referenceopen allclose all
Description of key information
One reliable experimental study is available (Klimisch reliability 2).
In this study, the ionisation constants of several polyphenols including the 4-ter-butyl pyrocatechol were investigated in water. For the 4-ter-butylpyrocatechol, the pKa1 and the pKa2 were determined as 9.53 and 14.0 respectively. Based on these dissociation constants, we can conclude that the test item is in neutral form (non ionised) up to a pH value of 7.53. Between 7.53 and 9 the test iem is present in majority under neutral and partially in its ionised form.
Key value for chemical safety assessment
- pKa at 20°C:
- 9.53
Additional information
As supporting data, the pKa values for 4-TBC have been also calculated by the SPARC model. The pKa values are 9.53 (for hydroxyl in position 2) and 9.73 (for hydroxyl in position 1) at a temperature of 25°C. The lowest value obtained is consitent with the lowest value determined in the experimental key study.
Another experimental study providing a pK value for the 4-ter-butylpyrocatechol is available (Corse et al 1951). However as the pK value was determined in a 40% dioxane solution, it was considered as not relevant and therefore not reported in this dataset.
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