N-(1,3-dimethylbutylidene)-5-[(1,3-dimethylbutylidene)amino]-1,3,3-trimethylcyclohexanemethylamine

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

28.07.2014 - 22.10.2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

GLP compliance:

yes

Specific details on test material used for the study:

Identification: CAS# 71077-09-3
Appearance/Physical State: Pale yellow liquid
Batch: 76200
Purity: 98.7%
Expiry Date: 30 April 2015
Storage Conditions: Room temperature in the dark

Radiolabelling:

no

Analytical monitoring:

yes

Buffers:

Buffer solution (pH)
Components
Concentration
(mmol dm-3)
4
Citric acid
0.6
Sodium chloride
0.4
Sodium hydroxide
0.7
7
Disodium hydrogen orthophosphate (anhydrous)
0.3
Potassium dihydrogen orthophosphate
0.2
Sodium chloride
0.2
9
Disodium tetraborate
0.1
Sodium chloride
0.2

Details on test conditions:

Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 0.50 mg/L in the three buffer solutions. A 1% co-solvent of acetonitrile was used to aid solubility.
The test solutions were split into individual vessels for each data point.
The solutions were shielded from light whilst maintained at the test temperature.
Sample solutions at pH 4, 7 and 9 were maintained at 70.0 ± 0.5 °C, 60.0 ± 0.5 °C, 50.0 ± 0.5 °C, 30.0 ± 0.5 °C and 20.0 ± 0.5 °C (as appropriate for each pH) for a suitable period of time in order to be able to calculate the half-life at each temperature.
3.5.2.2 Analysis of the Sample Solutions
The sample solutions were taken from the waterbath at various times and the pH of each solution recorded.
The concentration of the sample solution was determined by high performance liquid chromatography (HPLC).

Number of replicates:

Duplicate aliquots (A and B) of each sample solution were diluted by a factor of two using methanol.
Sample blanks
Methanol: relevant pH buffer solution (50:50 v/v)
Standards
Standard solutions of test item were prepared in methanol: purified water (50:50 v/v) covering a nominal concentration range of 0 to 0.50 mg/L, with a check standard at nominally 0.25 mg/L.
Matrix blanks
Methanol: purified water (50:50 v/v)

Positive controls:

not specified

Negative controls:

not specified

Transformation products:

yes

No.:

#1

No.:

#2

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

On discussions with the Sponsor, it was indicated that the test item is made by driving off water, and it is in equilibrium. Therefore, the ultimate hydrolysis products were considered to be the starting materials, isophorone diamine (IPDA) and methyl isobutyl ketone (MIBK).

% Recovery:

41.4

St. dev.:

5.6

pH:

4

Temp.:

50 °C

Duration:

4 h

% Recovery:

73.2

St. dev.:

2.2

pH:

4

Temp.:

60 °C

Duration:

4 h

pH:

7

Temp.:

20 °C

Remarks on result:

hydrolytically stable based on preliminary test

pH:

7

Temp.:

30 °C

Remarks on result:

hydrolytically stable based on preliminary test

pH:

9

Temp.:

20 °C

Remarks on result:

hydrolytically stable based on preliminary test

pH:

9

Temp.:

30 °C

Remarks on result:

hydrolytically stable based on preliminary test

Key result

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

0.138 h-1

Type:

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

Validity criteria fulfilled:

yes

Conclusions:

The rate constants and estimated half-lives at 25 °C of the test item are shown in the following table:
Table 3.16
pH
Rate constant (hr-1)
Estimated half-life at 25 °C
4
~ 0.138
~ 5 hours
7
-
< 2 hours
9
-
< 2 hours

Executive summary:

The sample blank solutions were noted to contain a significant response at approximately the retention time of the test item. Therefore, all of the sample concentrations have been corrected for the appropriate sample blank solution.

The detector response of the standards was noted to decrease over the course of the analysis runs. However, on review, the effect of this on the overall results was considered to be minor.

The limit of detection was somewhat variable run-to-run due to the method of detection (MS) used, but was based on approximately 2 times the baseline “noise” observed for the individual sample blank injections at approximately the retention time of the test item.

On comparison to the initial hydrolysis testing (see Appendix 3), the main difference was that the individual components of the test item could be seen in the chromatograms. The main problem with this was that the limit-of-quantitation was now much higher than that for the preliminary testing, with the result that rapid losses of test item due to hydrolysis quickly made most, if not all of the sample results, “none detected”.

The kinetics of the study has been determined to be consistent with that of a pseudo-first order reaction as the graphs of log10 concentration versus time are essentially straight lines.

It has been observed that the rate of hydrolysis increases with an increase in pH.

Key value for chemical safety assessment

Half-life for hydrolysis:

2 h

at the temperature of:

25 °C