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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.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:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Principles of method if other than guideline:
1. - Phase distribution studies (Conductometric method)
2. - Measurements of pH changes during titrations using glass electrodes (Titration method)
GLP compliance:
not specified
Dissociating properties:
yes
No.:
#1
pKa:
1
Temp.:
25 °C
Remarks on result:
other: Conductometric method
No.:
#2
pKa:
1.72
Temp.:
25 °C
Remarks on result:
other: Titration method

Assessment of the reliability of the quoted constant si given as "uncertain", where the estimated uncertainty is greater than 10 per cent of the value of K, i.e. ∆pK > +/- 0.04

Conclusions:
The pKa of dibutyl hydrogen phosphate is 1.0 at 25°C (Conductometric method) and 1.72 at 25°C (Titration method).
Executive summary:

The pKa of dibutyl hydrogen phosphate was 1.0 at 25°C determined in a phase distribution study (Conductometric method), and 1.72 at 25°C determined via measurements of pH changes during titrations using glass electrodes (Titration method).

Description of key information

The pKa of dibutyl hydrogen phosphate is 1.0 at 25°C (Conductometric method).

Key value for chemical safety assessment

pKa at 20°C:
1

Additional information

Several data on pKa for dibutyl hydrogen phosphatein the range of 0.98 - 1.72 are available, all indicating that dibutyl hydrogen phosphate exists predominantly in its deprotonated form under environmental conditions.

The most reliable value is the pKa of 1.0 at 25°C determined in a phase distribution study (Conductometric method).

Additionally the experimental dissociation constant of dibutyl hydrogen phosphate is supported by an estimated value. A pKa of 1.53 was estimated by ACD/pKa DB included in ACD/labs 7.00 Release. The result is in good correlation to the measured values.