dimethyl 1,2-benzenedicarboxylate;reaction mass of: 1,2-dimethylpropylidene dihydroperoxide

Partition coefficient

Link to relevant study record(s)

Reference

Endpoint:

partition coefficient

Type of information:

experimental study

Adequacy of study:

key study

Study period:

28 November 2001- 29 May 2002

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 117 (Partition Coefficient (n-octanol / water), HPLC Method)

Qualifier:

according to guideline

Guideline:

EU Method A.8 (Partition Coefficient)

GLP compliance:

yes

Type of method:

HPLC method

Partition coefficient type:

octanol-water

Analytical method:

high-performance liquid chromatography

Type:

log Pow

Partition coefficient:

0.27

Temp.:

24.5 °C

Remarks on result:

other: Minor component 1 (peak 1)

Type:

log Pow

Partition coefficient:

0.85

Temp.:

24.5 °C

Remarks on result:

other: Minor component 2 (peak 2)

Type:

log Pow

Partition coefficient:

1.6

Temp.:

24.5 °C

Remarks on result:

other: Major component (peak 3)

Type:

log Pow

Partition coefficient:

2.1

Temp.:

24.5 °C

Remarks on result:

other: Minor component 3 (peak 4)

Type:

log Pow

Partition coefficient:

3.2

Temp.:

24.5 °C

Remarks on result:

other: Minor component 4 (peak 5)

Type:

log Pow

Partition coefficient:

3.4

Temp.:

24.5 °C

Remarks on result:

other: Minor component 5 (peak 6)

Details on results:

RESULTS/CALCULATION METHOD
From the structural formula , the log Pow was calculated to be -0.95,0.22, 0.75 and 2.20 (Pow = 0.11, 1.66,5.62 and 158), using the Rekker calculation method.

RESULTS/HPLC METHOD
The chromatograms of the preliminary test showed a single peak and no test substance peaks with a retention time larger than 2,4-DDT.
Using 50/50 (v/v) methanol/Milli-Q water as the mobile phase, a 100 RP-18 column and a spectrophotometric detector set to read the absorbance at 210 nm, one large and five small test substance peaks were observed in the chromatograms of the 1099.4 mg/l test solution which were recorded for 110 minutes. The temperature of the mobile phase was 24.5 ± 1.0°C during the test. It was assumed that the large peak derives from the major component of the test substance whereas the small peaks derive from minor components in of the test substance.
The t0 (the retention time of the unretarded component) was determined to be 1.104 minutes as a mean value of both measurements (i.e. 1.104 and 1.104 minutes). The calculations were performed using not-rounded values. Therefore, some differences might be observed when re-calculating the k' values, the log k' values, the log Pow values and the Pow values.

The results of the Calculation method and the HPLC method are not in agreement. Since the HPLC method is a more accurate method than the Calculation method, the result of the HPLC method is reported as the partition coefficient (n-octanol/water), Pow.

Conclusions:

The log Pow value for the major component in the test substance is 1.6 at 24.5 ± 1.0°C. The log Pow values for five minor components are 0.27, 0.85, 2.1, 3.2 and 3.4 at 24.5 ± 1.0°C.
In this test, the major component has a log Pow of 1.6, which is in accordance with literature data indicating that the main component by weight, dimethylphthalate, has a log Pow of 1.6 (Ellington and Floyd, USEPA/600/S-96/001, Sept. 1996).
According to literature, the component 3-methyl-2-butanone has a log Pow of 0.84 (Hansch, C et al,1995).

Executive summary:

The determination of the partition coefficient (n-octanol/water) was based on the following guidelines:

OECD Guidelines for Testing of Chemicals, Guideline No. 117: "Partition coefficient (n-octanol/ water) High Performance Liquid Chromatography (HPLC) method" (adopted March 30, 1989).

EEC directive 92/69 EEC, Part A, Methods for the determination of physico-chemical properties, A.8: "Partition coefficient", EEC Publication no. L383, December 1992.

Since the substance is a mixture of compounds, the HPLC method was chosen for the determination of the partition coefficient (n-octanol/water). The Rekker calculation method was also performed.

Rekker calculation method

From the structural formula, the log Pow was calculated to be -0.95,0.22, 0.75 and 2.20 (Pow = 0.11, 1.66, 5.62 and 158).

HPLC method

The chromatograms of the preliminary test showed a single peak and no test substance peaks with a retention time larger than 2,4-DDT. Using 50/50 (vlv) methanol/Milli-Q water as the mobile phase, a 125 mm LiChrospher 100 RP-18 column (Merck) and a spectrophotometric detector set to read the absorbance at 210 nm, one large and five small test substance peaks were observed in the HPLC chromatograms. The large peak probably derives from the major component and the small peaks probably derive from minor components.

The corresponding Pow and log Pow values are:

Major component: Pow = 3.60 X 10 (log Pow = 1.6)

Minor component 1: Pow =1.84 (log Pow =0.27)

Minor component 2: Pow =7.06 (log Pow =0.85)

Minor component 3: Pow = 1.36 x 10^2 (log Pow = 2.1 )

Minor component 4: Pow = 1.65 X 10^3 (log Pow = 3.2)

Minor component 5: Pow = 2.47 X 10^3 (log Pow = 3.4)

The temperature of the mobile phase was 24.5 ± 1.0°C during the test.

Conclusion

The results of the Calculation method and the HPLC method are not in agreement. Since the HPLC method is a more accurate method than the Calculation method, the result of the HPLC method is reported as the partition coefficient (n-octanol/water), Pow. The log Pow value for the major component is 1.6 at 24.5 ± 1.0°C. The log Pow values for five minor components 0.27, 0.85, 2.1, 3.2 and 3.4 at 24.5 ± 1.0°C.

In this test, the major component has a log Pow of 1.6, which is in accordance with literature data indicating that the main component by weight, dimethylphthalate, has a log Pow of 1.6 (Ellington and Floyd, USEPA/600/S-96/001, Sept. 1996).

According to literature, the component 3-methyl-2-butanone has a log Pow of 0.84 (Hansch, C et al,1995).

Description of key information

From the structural formula, the log Pow was calculated to be -0.95,0.22, 0.75 and 2.20 (Pow = 0.11, 1.66, 5.62 and 158).

The results of the Calculation method and the HPLC method are not in agreement.

Since the HPLC method is a more accurate method than the Calculation method, the result of the HPLC method is reported as the partition coefficient (n-octanol/water), Pow. The log Pow value for the major component is 1.6 at 24.5 ± 1.0°C. The log Pow values for five minor components 0.27, 0.85, 2.1, 3.2 and 3.4 at 24.5 ± 1.0°C.
In this test, the major component has a log Pow of 1.6, which is in accordance with literature data indicating that the main component by weight, dimethylphthalate, has a log Pow of 1.6 (Ellington and Floyd, USEPA/600/S-96/001, Sept. 1996).
According to literature, the component 3-methyl-2-butanone has a log Pow of 0.84 (Hansch, C et al,1995).

EPIwin calculations for 1,2-dimethylpropylidene dihydroperoxide (monomer) CAS 13921-99-8 and Dimethyl 1,2-benzenedicarboxylate (dimer) CAS 33372-83-7 are as follows:

Monomer Log Kow: 0.80

Dimer Log Kow: 3.18

The concentration of the monomer in the multi-constituent is higher than that of the dimer, but in general substances with a higher log Kow are more toxic. As a worst case a log Kow of 3.4 (measured data) is used in the assessment, therefore.

Key value for chemical safety assessment

Log Kow (Log Pow):

3.4

at the temperature of:

24.5 °C