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EC number: 700-327-5 | CAS number: 1061328-86-6
- 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
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: study well documented, meets generally accepted scientific principles, acceptable for assessment
- Qualifier:
- no guideline followed
- Deviations:
- not applicable
- Principles of method if other than guideline:
- Persistence of chemical compounds is characterised by physical quantities such as equilibrium, stability constant (in the case of complexes - chelates) and the dissociation contant (for soluble salts, acids and bases). In the case of complexes the term dissociation constant does not apply, but a stability constant of complex can be determined instead. The following is a stability constant for FeHBED, which was based on the protonation constant of the chelating agent HBED by potentiometric, spectrophotometric methods and calculation programs.
- GLP compliance:
- no
- Dissociating properties:
- not determined
- Conclusions:
- Stability constant = 39.01
- Executive summary:
In the case of complexes the term dissociation constant does not apply, but a stability constant of the complex was determined instead in a non-GLP study (2009). A stability constant of 39.01 for FeHBED, which was based on the protonation constant of the chelating agent HBED by potentiometric, spectrophotometric methods in KCl supporting electrolyte (0.100 M) at 25.0 °C and calculation programs, was confirmed.
Reference
Protonation and thermodynamic stability constants of divalent metals ions with HJB, o,o-EDDHA and HBED chelating agents with HJB, o,o-EDDHA and HBED chelating agents:
Protonation constants | HJB | o,o-EDDHA | HBED |
[LH3-]/[H+]*[L4-] => logK1 | 12.36 | 11.94 | 12.64 |
[LH22-]/[H+]*[LH3-] => logK2 | 9.99±0.21 | 10.73 | 11.03 |
[LH3-]/[H+]*[LH22-] => logK3 | 8.21±0.29 | 8.66±0.04 | 8.34 |
[LH4]/[H+]*[LH3-] => logK4 | 4.79±0.30 | 6.18±0.06 | 4.40 |
Stability constants | HJB | o,o-EDDHA | HBED |
[CaL2-]/[Ca2+]*[L4-] | 8.28±0.07 | 7.29±0.30 | 9.29 |
[CaLH-]/[Ca2+]*[H+]*[L4-] | 17.39±0.23 | 16.77±0.33 | 17.98 |
[CaLH2]/[Ca2+]*[H+]2*[L4-] | 25.31±0.48 | 25.95±0.50 | 25.48 |
[MgL2-]/[Mg2+]*[L4-] | 8.95±0.10 | 9.76±0.05 | 10.51 |
[MgLH-]/[Mg2+]*[H+]*[L4-] | 17.83±0.01 | 18.18±0.15 | 18.66 |
[MgLH2]/[Mg2+]*[H+]2*[L4-] | 23.79±0.24 | 25.79±0.24 | 27.67 |
HBED presents a logK1 higher than o,oEDDHA, but similar to its analogue HJB. LogK2 is similar to that of o,oEDDHA and higher than in HJB, surely due to a higher interaction between the two phenolate groups in HJB. The amine groups protonation constants (logK3 and logK4) are similar to those of the HJB, but lower than those of the o,oEDDHA. It seems that the protonation of the tertiary amines (HJB and HBED) is more difficult than in the secondary amines (o,oEDDHA).
HBED/Ca2+stability constants are similar to those of o,oEDDHA and HJB but HBED/Mg2+ is more stable than HJB and o,oEDDHA chelates. The lower rigidity of HBED complexes than those the o,oEDDHA complexes is the cause of its higher constants. This effect seems to be more important that the effect of the methyl group in the HJB/Ca2+chelate, but no in the HJB/Mg2+one. At physiological pH the Ca2+predominant species with HBED are CaH2L0 and over pH 7.50 CaHL-. However the Mg2+ predominant species at physiological pH is MgHL- and at pH over 8.15 is MgL2 -.
The results of HBED/Fe3+stability constants compared with those of o,oEDDHA/Fe3+ and HJB/Fe3+ are presented in the table below. HBED/Fe3+ is the chelate with the higher stability. In all the cases, only the FeL- chelate is the predominant species at agronomic pHs. The o,oEDDHA/Fe3+ has two different diastereoisomers, forming the meso less stable chelates than HJB and the racemic more stables. Both diastereoisomers are less stable than HBED chelates.
Stability constants | HJB | o,o-EDDHA | rac-EDDHA | meso-EDDHA | HBED |
logKML | 34.45±0.04 | 35.09±0.28 | 35.86 | 34.15 | 39.01 |
logKMLH | 35.27±0.6 | 36.89±0.21 | 36.08 | 36.56 | 40.52 |
logKMLOH | - | 23.66±0.27 | 13.12 | 22.81 | - |
Description of key information
In the case of complexes the term dissociation constant does not apply, but a
stability constant of the complex was determined instead in a non-GLP study (2009). A stability constant of 39.01 for FeHBED, which was based on the protonation constant of the chelating agent HBED by potentiometric, spectrophotometric methods in KCl supporting electrolyte (0.100 M) at 25.0 °C and calculation programs, was confirmed.
Key value for chemical safety assessment
- pKa at 20°C:
- 39.01
Additional information
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