Butanal, reaction products with aniline

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

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:

yes

Remarks:

Due to the complex hydrolysis behaviour, the main test was performed at one temperature (70°C). Information for a second temperature (50°C) is available from the preleminary test.

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

Due to the complex hydrolysis behaviour, the main test was performed at one temperature (70°C). Information for a second temperature (50°C) is available from the preleminary test.

Principles of method if other than guideline:

Due to the complex hydrolysis behaviour, the main test was performed at one temperature (70°C). Information for a second temperature (50°C) is available from the preleminary test.

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Analytical monitoring:

yes

Buffers:

Buffer pH 4, Fa. Fluka, Citric acid/NaOH/NaCl, Art-Nr.: 33643
Buffer pH 7, Fa. Fluka, KH2PO4/Na2HPO4, Art-Nr.: 33646
Buffer pH 9, Fa. Fluka, Na2B4O7/HCl, Art-Nr.: 33648

Estimation method (if used):

Calculation of hydrolysis:
Hydrolysis was observed and calculated by determination of the HPLC-area units of corresponding to the concentrations of the test item in the test solutions.

Details on test conditions:

Preparation of the test solutions:
25.5 mg of the test item was dissolved in 100 ml acetonitrile. These stock solutions were 1:100 diluted with buffer solution pH 4 (respectively 7 and 9), leading to a test item concentration of 2.46 mg/l. Aliquots of the stock solution were taken to obtain individual vials for every test point. Preparation was carried out under nitrogen as flushing gas, to avoid oxygen. The vials were closed and incubated at 70 °C in a heat regulator under dark to avoid any photolytic effects.
The pH of the blank buffer solution was checked at the beginning of the test. Additionally the pH of the hydrolysis solution was measured at each test point. The temperature during the experiment was also checked at each test point. The calibration of aniline was verified daily at the level of 1.12 mg/l by using a control calibration solution. At each test point the hydrolysis solution was directly led to the chromatographic measurement.

Duration:

7 d

pH:

4

Temp.:

70 °C

Initial conc. measured:

ca. 2.6 mg/L

Duration:

28 d

pH:

7

Temp.:

70 °C

Initial conc. measured:

ca. 2.6 mg/L

Duration:

15 d

pH:

9

Temp.:

70 °C

Initial conc. measured:

ca. 2.6 mg/L

Preliminary study:

The preliminary test of water solubility of the test item corresponds to the OECD guideline No 105 'Water solubility'. A solubility of 5.2 mg/l of the test item in buffer solution pH 4 was observed. According to OECD TG 111 the concentration of the test item should not exceed 0.01 M or half of the saturation concentration of the water solubility. Therefore the half concentration of the solubility of the test item (2.6 mg/l) in buffer solution pH 4 was used for the hydrolysis tests. In compliance with OECD 111 Guideline no further solubility test with organic solvent additives > 1% v/v was performed.

Transformation products:

yes

No.:

#1

No.:

#2

pH:

4

Temp.:

70 °C

Remarks on result:

not determinable because of methodological limitations

pH:

7

Temp.:

70 °C

Remarks on result:

not determinable because of methodological limitations

pH:

9

Temp.:

70 °C

Remarks on result:

not determinable because of methodological limitations

Results of the hydrolysis:

Retention times of the HPLC peaks of the test item at pH 4 / 7 / 9:

HPLC-peak 1 = Aniline at approx. 4.1 minutes

HPLC-peak 2 = at approx. 7.3 minutes

HPLC-peak 3 = at approx. 12.7 minutes

Additional peak at approx. 13.8 minutes (only pH 7 and 9)

HPLC-peak 4 = at approx. 15.7 minutes

HPLC-peak 5 = at approx. 17.2 minutes

HPLC-peak 6 = at approx. 20.2 minutes

HPLC-peak 7 = at approx. 20.9 minutes

Values in area units of HPLC peaks

HPLC peakNo	unhydrolysed test item	pH 4		pH 7		pH 9
	dissolved in acetonitrile	first test point	last test point (7days)	first test point	last test point (28 days)	first test point	last test point (15 days)
1 (aniline)	5.3 (0.018 mg/l)	118.2 (0.37 mg/l)	66.4 (0.21 mg/l)	79.1 (0.25 mg/l)	136 (0.42 mg/l)	22.5(0.07 mg/l)	142(0.45 mg/l)
2*	n.d.	6.7	38.9	5.1	21.2	n.d.	21.0
3*	15.2	78.2	57.7	59.1	16.1	19.0	31.6
(ret.time 13.8 min)*	n.d.	n.d.	n.d.	12.8	19.6	12.9	28.0
4 (identified by GC/MS: 3 -ethyl-4 -propyl-quinoline)	22.1	24.5	369	21.8	197.3	21.4	53.5
5*	10.7	5.0	n.d.	n.d.	n.d.	n.d.	n.d.
6*	53.8	n.d.	n.d.	21.5	n.d.	48.5	n.d.
7*	59.2	n.d.	n.d.	23.6	n.d.	47.9	n.d.

n.d.= not detected (<limit of detection)

*Structure elucidation was tried with GC/MS and LC/MS but not successful

Validity criteria fulfilled:

yes

Remarks:

Verification of the calibration show stability of the chromatographic system. Recoveries of test item are in the range from 97.8 % to 101.0 % indicating a satisfying repeatability of the method applied to quantify the test item concentrations

Conclusions:

The test item degrades rapidly to anline and less rapidly to mainly 3 -ethyl-4 -propylquinoline. Therefore no half-life time and hydrolysis rate could be calculated.

Executive summary:

The hydrolysis behaviour was investigated at 70 °C and pH 4, pH 7 and pH 9 according to OECD TG 111. Additionally a preliminary test at 50 °C and pH 4, pH 7 and pH 9 was reported. The stability was monitored by HPLC analysis using UV-detection. The test item is a mixture of 6 main components, including aniline at low concentration. Three components degrade immediately and the hydrolysis product aniline was formed. One constituent increased immediately to a constant concentration. Another component increased also to a higher concentration and the structure of this component is identified by GC-MS, described in the report of the material balance (see file number 2011/0032/14). This hydrolysis product is 3 -ethyl-4 -propylquinoline (or isomeric form). The aniline concentration degraded at pH 4 and increased at pH 7 and 9. Furthermore two new peaks were observed during the abiotic degradation (hydrolysis) and they increased immediately to a constant concentration but could not be identified. At pH 4, pH 7, pH 9 and at the preliminary test at 50° the test item showed similiar degradation behavior.

The substance shows a complex hydrolysis behaviour. Part of the substance degrades rapidly to anline . Other constituentss of the substance are also degraded but somewhat slower forming the second main hydrolysis product 3 -ethyl-4 -propylquinoline. Due to this complex hydrolysis reaction no half-life could be calculated.

Description of key information

The hydrolytical behaviour of the substance is described in a test according to OECD 111 at 3 pH values (4, 7 and 9) (Currenta 2013). The reaction was found to be highly complex, and no rate constant or half lifes could be determined. Two main hydrolysis product could be identified: Aniline and 3-ethyl-4-propyl- quinoline.

Additional information

The hydrolysis behaviour can be discussed as follows:

1. The reaction mechanism at pH 4, 7 and 9 are simiilar. The reaction speed is decreasing from pH4 over pH7 to pH 9.

2. Formation of Aniline is the first hydrolysis step which occurs relatively fast even at room temperature. Howerver, the Aniline formed covers only about 30% of the original substance. When having reached this level, the concentration of Aniline remaines stable or decreases slightly.

3. Remaining constituents of the substance show a complex reaction pattern with components increasing and decreasing. It was technically not possible to identify the intermediates. The main final hydrolysis product is 3-ethyl-4-propyl- quinoline (or isomeric forms). As the reaction is relatively slow it was only performed at 70°C. At pH4, the formation of this product is complete after 1 day, at pH7 after about 21 days. At pH9 the reaction is slower.