1,3-bis(1-isocyanato-1-methylethyl)benzene

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From May 28, 2003 to June 11, 2003

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

no

GLP compliance:

yes

Radiolabelling:

no

Analytical monitoring:

yes

Buffers:

- pH: 1.2
- Composition of buffer:
Hydrochloric acid: 0.0065 mol/dm3
Potassium chloride: 0.005 mol/dm3

- pH: 4
- Composition of buffer:
Potassium hydrogen phthalate: 0.005 mol/dm3

- pH: 7
- Composition of buffer:
Disodium hydrogen orthophosphate (anhydrous): 0.003 mol/dm3
Potassium dihydrogen orthophosphate: 0.002 mol/dm3
Sodium chloride: 0.002 mol/dm3

- pH: 9
- Composition of buffer:
Disodium tetraborate: 0.001 mol/dm3
Sodium chloride: 0.002 mol/dm3

Details on test conditions:

TEST SYSTEM
- Type of test flasks: Stoppered glass flasks
- Lighting: Solutions were shielded from the light
TEST MEDIUM
- Preparation of samples: Prepared in stoppered glass flasks at a nominal concentration of 0.001 g/L in the four buffer solutions
- Identity and concentration of co-solvent: Acetonitrile (1 %)

Duration:

24 h

pH:

1.2

Initial conc. measured:

0.032 mg/L

Duration:

0.5 h

pH:

4

Initial conc. measured:

0.917 mg/L

Duration:

1 h

pH:

7

Initial conc. measured:

0.99 mg/L

Duration:

1 h

pH:

9

Initial conc. measured:

0.555 mg/L

Number of replicates:

Two

Positive controls:

no

Negative controls:

no

Statistical methods:

Not applicable

Preliminary study:

- Estimated half life at pH 4, 7 and 9 at 25 °C: < 1 d
- Hydrolysis after 2.4 h: > 50 %
- Results indicated the need of definitive test to estimate the rate constant and t1/2

Test performance:

Not applicable

Transformation products:

not measured

Details on hydrolysis and appearance of transformation product(s):

Not applicable

% Recovery:

>= 45.9 - <= 51.5

pH:

4

Temp.:

25 °C

Duration:

0.5 h

% Recovery:

>= 64 - <= 69.5

pH:

7

Temp.:

25 °C

Duration:

1 h

% Recovery:

>= 49 - <= 55.2

pH:

9

Temp.:

25 °C

Duration:

1 h

Key result

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

1.69 h-1

DT50:

0.41 h

Type:

(pseudo-)first order (= half-life)

Key result

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

1.9 h-1

DT50:

0.36 h

Type:

(pseudo-)first order (= half-life)

Key result

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

2.07 h-1

DT50:

0.34 h

Type:

(pseudo-)first order (= half-life)

Details on results:

TEST CONDITIONS
- pH, sterility, temperature and other experimental conditions maintained throughout the study: Yes

Validity criteria fulfilled:

yes

Conclusions:

Under the study conditions, rate constant and estimated half-life were found to be 1.692 h-1 and 0.410 h (at pH 4), 1.9044 h-1 and 0.364 h (at pH 7), and 2.0664 h-1 and 0.336 h (at pH 9), respectively. Under physiologically important conditions (pH 1.2, 37°C), the test substance was found to degrade almost instantaneously in the media, with only 3.45% of the fortified concentration remaining at the time zero initial analysis.

Executive summary:

A study was performed to assess the hydrolytic stability of the test substance according to OECD Guideline 111, in compliance with GLP. Based on the results of a preliminary study, the test was conducted at pH 4, 7 and 9 at 25 ± 0.5°C, and at pH 1.2 at 37 ± 0.5°C for 24 h. Under the study conditions, rate constant and estimated half-life were found to be 1.692 h-1 and 0.410 h (at pH 4), 1.9044 h-1 and 0.364 h (at pH 7), and 2.0664 h-1 and 0.336 h (at pH 9), respectively. Under physiologically important conditions (pH 1.2, 37°C), the test substance was found to degrade almost instantaneously in the media, with only 3.45% of the fortified concentration remaining at the time zero initial analysis (Woolley and Mullee, 2003).

Key value for chemical safety assessment

Half-life for hydrolysis:

0.4 h

at the temperature of:

25 °C

Additional information

A study was performed to assess the hydrolytic stability of the test substance according to OECD Guideline 111, in compliance with GLP. Based on the results of a preliminary study, the test was conducted at pH 4, 7 and 9 at 25 ± 0.5°C, and at pH 1.2 at 37 ± 0.5°C for 24 h. Under the study conditions, rate constant and estimated half-life were found to be 1.692 h-1 and 0.410 h (at pH 4), 1.9044 h-1 and 0.364 h (at pH 7), and 2.0664 h-1 and 0.336 h (at pH 9), respectively. Under physiologically important conditions (pH 1.2, 37°C), the test substance was found to degrade almost instantaneously in the media, with only 3.45% of the fortified concentration remaining at the time zero initial analysis (Woolley and Mullee, 2003).

The hydrolysis products of m-TMXDI are comparable to those of other aliphatic and aromatic diisocyanates. Under environmentally relevant conditions (i.e. low concentrations of m-TMXDI, pH = 7), an insoluble urea and possibly also polyurea are formed (Allnex, pers. comm.; Pemberton and Tury, 2004; Heimbachet al., 1996; Yakabeet al., 1999; Turyet al., 2003; cited in Environment Canada/Health Canada, 2008). In specific cases (i.e. high dispersion combined with low concentrations), tetramethyl-m-xylene diamine may also be produced (Sopac and Boltromejuk, 1974; cited in Environment Canada/Health Canada, 2008).

The structure of the urea and polyurea are presented in Figure 1.

Figure 1: Structure of the urea and possible polyurea formed by hydrolysis of m-TMXDI
under environmentally relevant conditions

The structure of tetramethyl-m-xylene diamine is presented in Figure 2.

Figure 2: Structure of tetramethyl-m-xylene diamine potentially formed by hydrolysis of m-TMXDI under specific conditions (i.e. high dispersion combined with low concentrations)

 

References

Environment Canada/Health(2008). Screening assessment for the challenge. Benzene, 1,3-bis(1-isocyanato-1-methylethyl)-(tetramethyl-m-xylylene diisocyanate). Chemical Abstracts Service Registry Number 2778-42-9.https://www.ec.gc.ca/ese-ees/9C2F9934-38D3-4940-A472-5DD238B6076D/batch2_2778-42-9_en.pdf.

Heimbach F, Jaeger K and Sporenberg W (1996).Fate and biological effects of polymeric MDI (4,4-diphenylmethane diisocyanate and homologues) in small artificial ponds. Ecotox Environ. Safety 33:143-153.

Pemberton D and Tury B (2004). TDI industry risk assessment: sections on physico-chemical properties, environmental exposures and environmental effects. GIL report 2004/E.

Sopac ED and Boltromejuk LP (1974). Gig. Sanit. 7:10-13.

Tury B, Pemberton D and Bailey RE (2003). Fate and potential environmental effects of methylenediphenyl diisocyanate and toluene diisocyanate released into the atmosphere. J. Air and Waste Manage. Assoc. 53:61-66.

Yakabe Y, Henderson KM, Thompson WCet al.(1999). Fate of methylenediphenyl diisocyanate and toluene diisocyanate in the aquatic environment. Environ. Sci. Technol. 33(15):2579-2583.