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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Physical & Chemical properties

Dissociation constant

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Administrative data

Link to relevant study record(s)

Reference
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)

Statistical factors: +/-0.30

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.

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

Additional information