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EC number: 253-733-5 | CAS number: 37971-36-1
Dissociation constant
Administrative data
Link to relevant study record(s)
- Endpoint:
- dissociation constant
- Type of information:
- calculation (if not (Q)SAR)
- Adequacy of study:
- key study
- Study period:
- 2009
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- accepted calculation method
- Reason / purpose for cross-reference:
- reference to other study
- Principles of method if other than guideline:
- No experimental determination but calculation of pKa.
- GLP compliance:
- no
- Dissociating properties:
- yes
- No.:
- #1
- pKa:
- >= 8.09 - <= 9.09
- Temp.:
- 20 °C
- Remarks on result:
- other: pKa (HL/H+L)
- No.:
- #2
- pKa:
- >= 4.85 - <= 5.04
- Temp.:
- 20 °C
- Remarks on result:
- other: pKa (H2L/H+HL)
- No.:
- #3
- pKa:
- >= 4.34 - <= 4.54
- Temp.:
- 20 °C
- Remarks on result:
- other: pKa (H3L/H+H2L)
- No.:
- #4
- pKa:
- >= 3.78 - <= 4.2
- Temp.:
- 20 °C
- Remarks on result:
- other: pKa (H4L/H+H3L)
- No.:
- #5
- pKa:
- >= 0.66 - <= 1.5
- Temp.:
- 20 °C
- Remarks on result:
- other: pKa (H5L/H+H4L)
- Conclusions:
- In total, 2-phosphonobutane-1,2,4-tricarboxylic acid can release 5 protons step by step. Each release is described by one equilibrium constant (pKa). Depending on the value, the acid dissociation constants (pKa values) indicate strong (#5), medium strong (#4, #3, #2) and weak (#1) acids.
The pKa values indicate neither very strong nor very weak acids. - Executive summary:
The calculation of the dissociation constants of 2-phosphonobutane-1,2,4-tricarboxylic acid in water was performed by software ACD ChemSketch ACD/Labs 7.00 Release, Product Version 7.05. Usually the resulting dissociation constants are calculated for 20°C.
2-phosphonobutane-1,2,4-tricarboxylic acid in water can release 5 protons step by step.
Each release is described by one equilibrium reaction or equilibrium constant (pKa):
H5L = H+H4L (pKa = 1.08 ± 0.42)
H4L = H+H3L (pKa = 3.99 ± 0.21)
H3L = H+H2L (pKa = 4.44 ± 0.10)
H2L = H+HL (pKa = 4.99 ± 0.14)
HL = H+L (pKa = 8.59 ± 0.50)
Depending on the pKa value, the acid dissociation constants indicate strong (pKs < 3.8), medium strong (pKs < 7.2) and weak (pKs < 16) acids.
The pKa values indicate neither very strong nor very weak acids.
Reference
Statistical factors: +/-0.30
Description of key information
The calculation of the dissociation constants of 2-phosphonobutane-1,2,4-tricarboxylic acid in water was performed by software ACD ChemSketch ACD/Labs 7.00 Release, Product Version 7.05. Usually the resulting dissociation constants are calculated for 20°C.
2-phosphonobutane-1,2,4-tricarboxylic acid in water can release 5 protons step by step.
Each release is described by one equilibrium reaction or equilibrium constant (pKa):
H5L = H+H4L (pKa = 1.08 ± 0.42)
H4L = H+H3L (pKa = 3.99 ± 0.21)
H3L = H+H2L (pKa = 4.44 ± 0.10)
H2L = H+HL (pKa = 4.99 ± 0.14)
HL = H+L (pKa = 8.59 ± 0.50)
Depending on the pKa value, the acid dissociation constants indicate strong (pKs < 3.8), medium strong (pKs < 7.2) and weak (pKs < 16) acids.
The pKa values indicate neither very strong nor very weak acids.
Key value for chemical safety assessment
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