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Dissociation constant

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Reference
Endpoint:
dissociation constant
Type of information:
(Q)SAR
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method
Justification for type of information:
QSAR prediction: migrated from IUCLID 5.6
Principles of method if other than guideline:
The acronym for the (Q)SAR SPARC stands for:-

SPARC
Performs
Automated
Reasoning in
Chemistry

The (Q)SAR was developed at the University of Georgia through grants from USEPA.

The senior developers were:
S.W. Karickhoff (USEPA retired)
L.A. Carreira (Professor University of Georgia)
S.H. Hilal (USEPA)


Several endpoints are assessed within SPARC. For the determination of pKa the major reference was:-

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.

Overall modeling approach is outlined in more detail in:

Carreira, L. A., S. Hilal and S. W. Karickhoff, "Estimation of Chemical Reactivity Parameters and Physical Properties of Organic Molecules Using SPARC," (Book Chapter) Theoretical and Computational Chemistry, Quantitative Treatment of Solute/Solvent Interactions, Eds. P. Politzer and J. S. Murray, Elsevier Publishers, 1994.
Dissociating properties:
yes
No.:
#1
pKa:
11.91
Remarks on result:
other: Result based on Q(S)AR

Mechanistic Output for the Microscopic pKa

Subs are shown as SubType:[SubAnchorAtom]

Effect / Sub methyl:[C12] methyl:[C8] whole total
RESONANCE     3.12 3.12
SIGMA       0.00
FIELD       0.00
PI_INDUCTION -0.06 -0.06   -0.12
HYDRATION     -0.62 -0.62
TOTAL_PERTURBATION       2.38
REFERENCE       14.30
CALCULATED_PKA       11.91
Conclusions:
Using SPARC Version 4.5 online calculator (Listed in Table R7.1-3 of REACH Guidance document R7) the dissociation constant for 2,6-DTBP was determined to be pKa 11.91.
Executive summary:

Using SPARC Version 4.5 online calculator (Listed in Table R7.1-3 of REACH Guidance document R7) the dissociation constant for 2,6-DTBP was determined to be pKa 11.91.

Reference

1) pKa: 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.

Description of key information

Using the Q(S)AR SPARC Version 4.5 online calculator, the dissociation constant for 2,6-DTBP was determined to be pKa 11.91.

Key value for chemical safety assessment

pKa at 20°C:
11.91

Additional information