p-(trifluoromethoxy)phenyl isocyanate

Hydrolysis

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

other information

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

The stability of isopropylisocyanat in an aqueous test solution was investigated. Test conditions simulate those used in ecotox testing according to EU Method C.3 'Algal inhibition test'.

GLP compliance:

no

Remarks:

but in compliance with general principles of GLP rules.

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

- 5 different sampling times from 0 to 20 hours
- Analysis was performed immediately

Buffers:

buffer solution pH 7.0: 296.3 mL NaOH 0.1 mol/L + 500 mL Sodiumdihydrogenephosphate 0.1 mol/L adjusted to 1000 mL deionised water

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: Erlenmeyer flask 300 mL, with stopcock
- Lighting: radiation lamp, 11 Watt, 8000 lux, measured on the surface of the flask
- The test soulution and the head space were air saturated

TEST MEDIUM
- Kind and purity of water: deinoised water, e.g. purified over a Millipore system
- Preparation of test medium: the test compound (6 mg) was weighed in an Erlenmeyer flask and dissolved in 300 mL of buffer solution pH 7 by means of an ultrasonic bath (15 min). The resulting concentration was 20 mg/L. The Liquid was examined visually for undissolved particles, but was obviously clear.

Duration:

20 h

pH:

7

Temp.:

25 °C

Initial conc. measured:

20 mg/L

Number of replicates:

1

Positive controls:

yes

Remarks:

Isopropylamine

Transformation products:

yes

No.:

#1

% Recovery:

86

pH:

7

Temp.:

25 °C

Duration:

0 h

pH:

4

pH:

7

Temp.:

25 °C

DT50:

< 1 h

pH:

9

Degradation products (CAS No./EC No./EINECS Name): 75-31-0     200-860-9 isopropylamine

At sampling period 0 hours, 11.9 mg/l isopropylamine were found. This  value corresponds to about 86 % of the theoretical concentration  (complete degradation of 20 mg/l isopropyl isocyanate would yield 13.9  mg/l isopropylamine). Obviously, already during the solution process of  isopropyl isocyanate in water (15 minutes in an ultrasonic bath),  hydrolysis occurs nearly completely. At sampling periods 1, 2, 3, and 20  hours, the concentration of isopropylamine is only in the range of 6-7  mg/l. However, isopropylamine is known to be chemically stable under the  test conditions. Probably, some substance has been lost due to its  volatility. Under the mentioned test conditions, isopropyl isocyanate  degrades rapidly with a half life period of less than 1 hour yielding the  only metabolite isopropylamine

Validity criteria fulfilled:

not applicable

Remarks:

no guideline study was performed

Conclusions:

Test item degrades rapidly with a half live period of less than 1 hour (Bayer, 2003).

Executive summary:

The stability of isopropyl isocyanate in an aqueous test solution was investigated. Test conditions simulate those used in ecotox testing according to EU Method C.3 'Algal inhibition test'. Isopropyl isocyanate degrades rapidly with a half live period of less than 1 hour (Bayer, 2003).

Reference 2

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

other information

Study period:

2004

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Principles of method if other than guideline:

Examination of the stability under conditions simulating those in the environment (pH 7, presence of light and air)

GLP compliance:

no

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products: samples were taken after 0, 1, 2, 4, 6 and 70 h
- Sampling method: pipette
- Sample storage conditions before analysis: analysis was performed immedeately after sampling

Transformation products:

yes

No.:

#1

pH:

7

Temp.:

25 °C

DT50:

7.3 h

The test compound is degradable in aqueous solutions: 
a) Preparation of the test solution: vigorous agitation and ultrasonification for 10 minutes in order to dissolve 4-chlorophenyl isocyanate (target concentration 10 mg/l, 0.0651 mmol/l) leads to a rapid degradation of the test compound. More than 50% of the original amount of the test compound has been converted to 4-chloroaniline (4.39 mg/l, 0.0344 mmol/l) at time 0.
b) During the test, the test solution is allowed to stand still without any stirring or ultrasonification. The concentration of 4-chloroaniline increases continuously whereas 4-chlorophenyl isocyanate disappears in the same manner. Assuming a kinetic function of first order, a half life period of 7.3 hours can be calculated. After 70 h, the test was terminated. At this time, the test compound was completely converted to 4-chloroaniline.

Validity criteria fulfilled:

not applicable

Remarks:

no guideline study was performed

Conclusions:

Over the test duration of 70 h, the concentration of the test substance continuously decreased yielding a half-live of 7.3 h. 1-amino-4-chlorobenzene was identified as the only hydrolysis product (Bayer Industry Services, 2004).

Executive summary:

The stability of 1-chloro-4-isocyanatobenzene under conditions simulating those in the environment was tested meaning a pH of 7 as well as the presence of air and light. The test substance was dissolved in a buffer solution and subsequently keept at a temperature of 25 °C and ilumination. Samples were periodically taken and measured by the means of HPLC. Over the test duration of 70 h, the concentration of the test substance continuously decreased yielding a half-live of 7.3 h. 1-amino-4-chlorobenzene was identified as the only hydrolysis product (Bayer Industry Services, 2004).

Description of key information

The stability of an other isocyanate, isopropyl isocyanate, was tested in an aqueous test solution showing a rapid degradation (half live less than 1 hour). Further the stability of 1-chloro-4-isocyanatobenzene in a second test yielded a half-life of 7.3 h. The only hydrolysis products of both isocyanates were found to be the corresponding amines. These results support the expert statement attached in section 13 that a rapid hydrolysis in water with the corresponding amine as degradation product takes place. 

Key value for chemical safety assessment

Half-life for hydrolysis:

1 h

at the temperature of:

25 °C

Additional information

Isocyanates are known to rapidly hydrolyse under the formation of the corresponding amine as well as solid polyurea compounds *. However, the insoluble inert polyurea is not assumed to cause environmental hazards due to the reduced uptake of high molecular mass compounds, whereas the amine is assumed to be the ecotoxicological relevant species. Concluding, tests performed using the corresponding amine can equally be used to assess the ecotoxicological hazards of isocyanates assuming the complete transfer of the isocyanate into the corresponding amine while neglecting the formation of a certain fraction ecotoxicological not active polyurea compounds. An underestimation of environmental hazards is thus avoided supporting a conservative and thus protective hazard assessment.

* Bayer Industry Services (2004). 4-chlorophenyl-isocyanate: Investigation on Stability in Aqueous Test Solutions. Project No: 200300181. Leverkusen, Germany.

Bayer Industry Services (2003). Isopropylisocyante: Investigation on Stability in Aqueous Test Solutions. Project No: 200300095. Leverkusen, Germany.