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Physical & Chemical properties

Dissociation constant

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Description of key information

It can be concluded that in the conditions of the test performed according to the OECD guideline 112, no pK can be determined for TETRAMETHYLTHIURAM MONOSULFIDE.
However, according to 2 QSAR methods, dissociation constant of TMTM (tetramethylthiurame monosulphide) is found to be very low : lower to 2 and TMTM is mainly not dissociated in water.

Key value for chemical safety assessment

pKa at 20°C:
2

Additional information

The Dissociation Constants in Water (Titration Method) of the test item TETRAMETHYLTHIURAM MONOSULFIDE was studied according to the OECD guideline 112.During the analysis, the temperature was 24.7 +/- 1 °C.The pH of the 10-3 M solution of TETRAMETHYLTHIURAM MONOSULFIDE was 5.86.Titration curve of this solution by a solution of NaOH 0.01 mole/L did not show any equivalence point.It can be concluded that in the conditions of the test, no pK can be determined for TETRAMETHYLTHIURAM MONOSULFIDE.

However,

  • According to a calculation made with ACD labs software, pKa of tetramethylthiuram monosulphide is about 0.43-1.43.
  • According to SPARC, dissociation constant of TMTM (tetramethylthiurame monosulphide) is found about -4.3 (calculation). TMTM could not be dissociated in water. Finally we conclude that TMTM has got a pKa very low - probably lower to 2, and product is mainly not ionized.