1,8-naphthylenediamine

Hydrolysis

Administrative data

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 05 April 2019 to 06 July 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2020

Report date:

2020

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

All deviations stated as non-critical

Test guideline 2

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

yes

Remarks:

All deviations stated as non-critical

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

1,8-naphthylenediamine

EC Number:

207-529-8

EC Name:

1,8-naphthylenediamine

Cas Number:

479-27-6

Molecular formula:

C10H10N2

IUPAC Name:

naphthalene-1,8-diamine

Constituent 2

Reference substance name:

1,8-Naphthylendiamin

IUPAC Name:

1,8-Naphthylendiamin

Constituent 3

Reference substance name:

1,8-Naphthylendiamin

IUPAC Name:

1,8-Naphthylendiamin

Details on test material:

- Purity: 99.6 %

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source: Naoki Yamamoto, APIS & intermediates, API Corporation, 1-13-4 Uchi-kanda, Japan. Batch F71006
- Purity, 99.4%:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Room temperature (20 ± 5°C), keep tightly closed and away from light, heat and all sources of ignition and oxidizing agents in a dry and well-ventilated area
- Homogeneous
- Stability: unknown
- Solubility <0.1 g/L water:
- Reactivity of the test material with the incubation material used (e.g. plastic ware): not known

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- The test item was ground finely before usage

Radiolabelling:

no

Study design

Analytical monitoring:

yes

Remarks:

Analytical validation report VB17111002G926 is attached

Details on sampling:

- Sampling intervals for the parent (Tiers 1 and 2) and transformation products (Tier 3):
Tier 1 :
50.0 – 50.1 °C,
pH 4.0, 7.0 and 9.0
t=0h and t=120.5h (5d)

Tier 2:
12 °C - pH 4 - t=0, 21, 476, 575, 668 and 719 h
12 °C - pH 7 - t=0, 431, 530, 623, 694 and 790 h
12 °C - pH 9 - t=0, 139, 209, 360, 451, 550, 619, 669 and 714 h
25 °C - pH 4 - t=0, 164, 234, 476, 575, 668 and 719 h
25 °C - pH 7 - t=0, 340, 530, 603, 623, 649, 694 and 790 h
25 °C - pH 9 - t=0, 71.9, 115, 139, 169, 209, 285, 305, and 332 h
50 °C - pH 4 - t=0, 43.5,67.5, 73.6, 96.8, 140, 162, 194, 214, 234 and 310 h
50 °C - pH 7 - t=0, 117, 189, 333, 431, 530, 603, 623 and 694 h
50 °C - pH 9 - t=0, 23.5, 42.5, 48.6, 64.3, 71.8, 91.7, 116, 120 and 122 h

Tier 3 :
50 °C,
t=0h and t=5d for pH 9
t=0h and t=28d for pH 7
t=0h and t=10d for pH 4

- Sampling method: validation report VB17111002G926 (see attached)
- During hydrolysis turbidity in the samples occurred. Therefore, the following samples were centrifuged at 6000 rpm for 5 minutes:
Samples pH 4 at 50 °C with sampling times 213.5 h and 309.5 h. Samples pH 9 at 50 °C with sampling times 116.7 and 119.8 h. Samples pH 9 at 25 °C with sampling times 284.5, 304.5 and 331.5 h.
The supernatant of the centrifuged samples was used for the measurements.
Test item was filled up with hydrolysis buffer/water mixture 50/50 % (v/v) in a flask and treated with ultrasonic. These solutions with nominal concentration 380 mg/L were sterile filtered (with PTFE filters 0.2 µm pore size) into sterile vials.
The test vessels were then purged with sterile Argon to remove dissolved oxygen and then tightly closed with PTFE seals. The closed vials were incubated at a set temperature over a defined time period.
Samples were analysed before and after incubation

Buffers:

- pH: 4
CH3COOH, 2 M 80 mL
CH3COONa 40 mL
Demineralised water ad 1000 mL
Final pH value, (adjusted with 2 M CH3COOH or 2 M NaOH) 4.0

- pH: 7
KH2PO4 8.7088 g
Demineralised water 500 mL
NaOH, 2 M 14.9 mL
Demineralised water ad 1000 mL
Final pH value, (adjusted with 2 M NaOH) 7.0

- pH: 9
H3BO3 3.0930 g
KCl 3.7296 g
Demineralised water 500 mL
NaOH, 2 M 10.75 mL
Demineralised water Ad 1000 mL
Final pH value, (adjusted with 2 M NaOH) 9.0

Estimation method (if used):

The concentration of 1,8-Diaminonaphthalene chip in the solution was determined using the following equation:
"c" _"measured" " [mg/L] =" "(Measured value - a)" /"b" * (100 % / QC Recovery Rate [%]) * dilution factor

with
a = intercept
b = slope
"QC recovery in %" = "measured concentration" /"nominal concentration" *100 %

QC Recovery rate is taken into account, if necessary.

Hydrolysis
Hydrolysis in % was calculated from the following equation:
"H = " ("1-" "c" _"t" /"c" _"0" )"*100%"
ct concentration at time t
c0 concentration at time 0
Kinetic Parameters
Hydrolysis refers to a reaction of a substance RX with water:
RX + H2O  ROH + RX
Since H2O is present in great excess, kinetic usually can be considered as being first order. The corresponding equation for the rate of hydrolysis is calculated from:
rate = k * [RX]
A hydrolysis constant of pseudo-first order should be described as function of temperature. The rate constant kobs (k observed) at a defined pH and temperature is the mean of k at each time point t which is calculated using the following equation

"k" _"obs,i" "=" "1" /"t" "*ln" "c" _"0" /"c" _"t"

t time [h]
c0 concentration at time point 0 h
ct concentration at time point t

The half-life (t1/2) of the compound at a defined pH and temperature is calculated from:

"t" _"1/2" "=" "ln2" /"k" _"obs,i"

Calculation is performed using the Arrhenius equation, whose coefficients A and B are derived from the plot ln (k) vs. 1/T. Additionally, kobs was calculated as sum of acid catalysed, base catalysed and neutral hydrolysis:


kneutr hydrolysis rate at pH 7
kOH hydrolysis rate at pH 9
ln Ai intercept of each graph ln ki against 1/T
-Bi slope of each graph ln ki against 1/T
Ai exponential of ln Ai
T temperature in K

Slope and intercept for each pH were generated from linear regression of ln ki against 1/T:

ln ki = - Bi / T + ln Ai

Details on test conditions:

Tier 1 concentrations

Duration of test

Duration of test 1

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

346 mg/L

Remarks:

Target dose of 380 mg/L represents a 91.0% recovery

Duration of test 2

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

368 mg/L

Remarks:

A target dose of 380 mg/L represents a 96.96% recovery

Duration of test 3

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

376 mg/L

Remarks:

A target dose of 380 mg/L represents a 99.05% recovery

Number of replicates:

2

Positive controls:

no

Negative controls:

yes

Results and discussion

Preliminary study:

Tier 1 :
After five days (120.5 h) at 50 °C, the concentrations of the test item lay below 90% of the nominal start concentration at all three pH values. The test item was considered unstable and Tier 2 had to be conducted.
The highest decrease was at pH 9 with 81.2 %, whereas at pH 7 the decrease was only 14.5 %.

Test performance:

Deviations from the study plan (and guideline) :
•Deviating from nominal temperature 50 ± 0.5 °C the lowest temperature was 48.4 °C for pH 7 due to a power failure. This was stated as uncritical, because deviation occurred for a short time only.
•Test duration was 33 d instead of 30 d for pH 7 hydrolysis buffer solutions at 12 °C and at 25 °C due to organizational reason. This was stated as uncritical, because the result is definite.
•For the evaluation at pH 4, 25°C only 2 points were used for evaluation, because only two sampling points lay in the range 10 – 90 % degradation. This was accepted, because otherwise the measurements of pH 4 could not have been used for further evaluation (calculations using the ARRHENIUS equation).
The deviations were signed and assessed by the study director on 07. Aug. 2019.
Additionally, the following deviation from the study plan was ascertained:
•Deviating from nominal temperature 50 ± 0.5 °C the temperature range was 49.7 – 50.8°C due to insufficient temperature control. This was stated as uncritical, because the deviation was small.
•Deviating from nominal temperature 50 ± 0.5 °C the lowest temperature was 47.4 °C for pH 4 (additional experiment) due to insufficient temperature control. This was stated as uncritical, because deviation occurred for a short time only.
•Deviating from the study plan for the preparation of some hydrolysis buffers instead of demineralised water, water with analytical grade was used due to an error. This was stated as uncritical, because the used water was analytical grade and therefore sufficient.

Transformation products:

yes

Identity of transformation products

Identity of transformation products 1

No.:

#3

Reference

Reference substance name:

Unnamed

IUPAC name:

2-Methyl-1H-perimidine

CAS number:

5157-10-8

Molecular formula:

C12H10N2

Molecular weight:

182.2

SMILES notation:

CC1=NC2=CC=CC3=C2C(=CC=C3)N1

Identity of transformation products 2

No.:

#2

Reference

Reference substance name:

Unnamed

IUPAC name:

1H-Perimidine

CAS number:

204-02-4

Molecular formula:

C11H8N2

Molecular weight:

168.2

SMILES notation:

C1=CC2=C3C(=C1)NC=NC3=CC=C2

Identity of transformation products 3

No.:

#1

Reference

Reference substance name:

Unnamed

IUPAC name:

1,1’-Hydrazonaphthyl-8,8’Diamine

Molecular formula:

C20H18N4

Molecular weight:

314.4

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

Tier 3 - 50 °C for 5 days, pH 4, 7 and 9.
The content of one vial of each pH value was dissolved completely by addition of solvent. The clear solutions were measured with HPLC-UV-MS-MS using the same analytical method as for the HPLC-UV measurements.
The solutions, diluted after hydrolysis, were compared with freshly prepared test item solutions with nominal concentration 380 mg/L test item in the hydrolysis buffer/water mixtures (50/50 % (v/v)).
The relevant peaks were identified using the UV chromatograms. UV peaks were examined for their MS spectrum.
For the identification of degradation products > 10% of the original test item concentration, measurements with HPLC-UV-MS-MS, GC-MS and FT-IR were performed. Because sediment was formed after hydrolysis, test item solutions after hydrolysis were diluted with acetonitrile to give clear solutions for HPLC-UV-MS-MS measurements. Other flasks, containing test item solution after hydrolysis, were filtered and the residue was examined after dis-solution with GC-MS.
Substances, detected as degradation products, were similar for the three pH values.
The main substance in hydrolysed solutions was 1,8-Naphthalenediamine (the test substance) or a substance which shows very similar characteristics. Probably precipitation of the hydrated test item in dependence of pH, temperature and time occurred. This process was not reversible after ultrasonic treatment.
Several degradation products were detected with HPLC-UV-MS-MS and GC-MS. Products greater than 10%:
Only the presumed dehydration product 1,1’-Hydrazonaphthyl-8,8’Diamine (C20H18N4) was detected with UV signal higher than 10 % of the initial test item concentration. This was proposed by mass spectroscopy, but no analytical standard was available to confirm this assignment.
Products less than 10%:
1H-Perimidine (C11H8N2) was identified by comparison with a reference standard.
2-Methyl-1H-Perimidine was also suggested by mass spectroscopy, but no analytical standard was available to confirm this assignment.
The identity of other minor components were suggested by mass spectroscopy, but the proposed structures were considered to be implausible as hydrolysis products or were a reaction product with the acetone used for extraction.

A proposed hydrolysis pathway is attached.

Total recovery of test substance (in %)

Total recovery of test substance (in %) 1

% Recovery:

91

pH:

9

Temp.:

50 °C

Duration:

0 h

Total recovery of test substance (in %) 2

% Recovery:

96.96

pH:

7

Temp.:

50 °C

Duration:

0 h

Total recovery of test substance (in %) 3

% Recovery:

99.05

pH:

4

Temp.:

50 °C

Duration:

0 h

Dissipation DT50 of parent compound

Dissipation DT50 of parent compound 1

pH:

9

Temp.:

12 °C

Hydrolysis rate constant:

0.001 h-1

DT50:

745.1 h

St. dev.:

178

Type:

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

Dissipation DT50 of parent compound 2

pH:

7

Temp.:

12 °C

Remarks on result:

not determinable

Remarks:

Test item was stable under these conditions and so calculation of kinetic constants was not possible

Dissipation DT50 of parent compound 3

pH:

4

Temp.:

12 °C

Remarks on result:

not determinable

Remarks:

Test item was stable under these conditions and so calculation of kinetic constants was not possible

Dissipation DT50 of parent compound 4

pH:

9

Temp.:

25

Hydrolysis rate constant:

0.003 h-1

DT50:

202.1 h

St. dev.:

64.5

Type:

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

Dissipation DT50 of parent compound 5

pH:

7

Temp.:

25 °C

Remarks on result:

not determinable

Remarks:

Test item was stable under these conditions and so calculation of kinetic constants was not possible

Dissipation DT50 of parent compound 6

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

0 h-1

DT50:

3 791.6 h

St. dev.:

549.6

Type:

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

Dissipation DT50 of parent compound 7

pH:

9

Temp.:

50 °C

Hydrolysis rate constant:

0.014 h-1

DT50:

48.7 h

St. dev.:

10.1

Type:

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

Dissipation DT50 of parent compound 8

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

0.002 h-1

DT50:

450.2 h

St. dev.:

104

Type:

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

Dissipation DT50 of parent compound 9

pH:

4

Temp.:

50 °C

Hydrolysis rate constant:

0.004 h-1

DT50:

189.5 h

St. dev.:

93.5

Type:

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

Details on results:

Kinetic constants were not evaluated at 12 °C for pH 4 and pH 7 and at 25 °C for pH 7. The test item was stable under these conditions.

Because for pH 7 only one data point was evaluable (at 50°C), kobs at a temperature of 20 °C (293.15 K) was calculated using the ARRHENIUS equation based on the results of pH 4 and pH 9 only.
The hydrolysis constants obtained at 25 °C fit very well the ARRHENIUS equation, indicating that the reaction is indeed following pseudo-first order kinetics.
The hydrolysis mechanism is dependent from the pH value. The test item is most stable at pH 7 and most unstable at pH 9. Only at 50°C hydrolysis was determined over the test period at pH 7, whereas hydrolysis was determined at 12, 25 and 50°C for pH 9.
Using the ARRHENIUS equation, kobs and half-life of 1,8-Diaminonaphthalene chip at 20 °C (293.15 K) were calculated as:
kobs (293.15 K)= 0.002048 h-1
t1/2 (293.15 K) = 338.5 h

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The hydrolysis of 1,8-Diaminonaphthalene chip was determined in three experiments (Tier 1, Tier 2 and Tier 3) according to the OECD 111 Guideline.

Tier 1

After five days (120.5 h), the concentrations of the test item lay below 90% of the start concentration at all three pH values (Tier 1) after incubation for 5 d at 50 °C. The test item was considered unstable and Tier 2 had to be conducted.

Tier 2

Evaluation of experiment 2 (Tier 2) showed temperature dependency of the hydrolysis.

Kinetic constants were not evaluated at 12 °C for pH 4 and pH 7 and at 25 °C for pH 7. The test item was stable under these conditions.

Using the experimentally determined kobs for each pH and temperature, temperature dependency was calculated.

Because for pH 7 only one data point was evaluable (at 50°C), kobs at a temperature of 20 °C (293.15 K) was calculated using the Arrhenius equation based on the results of pH 4 and pH 9 only. The hydrolysis constants obtained at 25 °C fit very well the Arrhenius equation, indicating that the reaction is indeed following pseudo-first order kinetics.

The hydrolysis mechanism is dependent from the pH value. The test item is most stable at pH 7 and most instable at pH 9. Only at 50°C hydrolysis was determined over the test period at pH 7, whereas hydrolysis was determined at 12, 25 and 50°C for pH 9.

Using the Arrhenius equation, kobs and half-life of 1,8-Diaminonaphthalene chip at 20 °C (293.15 K) were calculated as:

kobs (293.15 K)= 0.002048 h-1

t1/2 (293.15 K) = 338.5 h


Tier 3 - 50 °C for 5 days, pH 4, 7 and 9.

The solutions, diluted after hydrolysis, were compared with freshly prepared test item solutions with nominal concentration 380 mg/L test item in the hydrolysis buffer/water mixtures (50/50 % (v/v)).
The relevant peaks were identified using the UV chromatograms. UV peaks were examined for their MS spectrum.
For the identification of degradation products > 10% of the original test item concentration, measurements with HPLC-UV-MS-MS, GC-MS and FT-IR were performed.
Substances, detected as degradation products, were similar for the three pH values.
The main substance in hydrolysed solutions was 1,8-Naphthalenediamine (the test substance) or a substance which shows very similar characteristics.
Several degradation products were detected with HPLC-UV-MS-MS and GC-MS.

Products greater than 10%:
Only the presumed dehydration product 1,1’-Hydrazonaphthyl-8,8’Diamine (C20H18N4) was detected with UV signal higher than 10 % of the initial test item concentration. This was proposed by mass spectroscopy, but no analytical standard was available to confirm this assignment.


Products less than 10%:
1H-Perimidine (C11H8N2) was identified by comparison with a reference standard.
2-Methyl-1H-Perimidine (C12H10N2) was also suggested by mass spectroscopy, but no analytical standard was available to confirm this assignment.


A proposed hydrolysis pathway is attached.

Executive summary:

The hydrolysis of 1,8-Diaminonaphthalene chip was determined in three experiments (Tier 1, Tier 2 and Tier 3) according to the OECD 111 Guideline.

Tier 1

After five days (120.5 h), the concentrations of the test item lay below 90% of the start concentration at all three pH values (Tier 1) after incubation for 5 d at 50 °C. The test item was considered unstable and Tier 2 had to be conducted.

Tier 2

Evaluation of experiment 2 (Tier 2) showed temperature dependency of the hydrolysis.

Kinetic constants were not evaluated at 12 °C for pH 4 and pH 7 and at 25 °C for pH 7. The test item was stable under these conditions.

Using the experimentally determined k_obs for each pH and temperature, temperature dependency was calculated.

Because for pH 7 only one data point was evaluable (at 50°C), k_obs at a temperature of 20 °C (293.15 K) was calculated using the Arrhenius equation based on the results of pH 4 and pH 9 only. The hydrolysis constants obtained at 25 °C fit very well the Arrhenius equation, indicating that the reaction is indeed following pseudo-first order kinetics.

The hydrolysis mechanism is dependent from the pH value. The test item is most stable at pH 7 and most instable at pH 9. Only at 50°C hydrolysis was determined over the test period at pH 7, whereas hydrolysis was determined at 12, 25 and 50°C for pH 9.

Using the Arrhenius equation, k_obs and half-life of 1,8-Diaminonaphthalene chip at 20 °C (293.15 K) were calculated as:

k_obs (293.15 K)=       0.002048 h^-1

t_1/2 (293.15 K) =        338.5 h

 

Tier 3 - 50 °C for 5 days, pH 4, 7 and 9.
 
The solutions, diluted after hydrolysis, were compared with freshly prepared test item solutions with nominal concentration 380 mg/L test item in the hydrolysis buffer/water mixtures (50/50 % (v/v)).
The relevant peaks were identified using the UV chromatograms. UV peaks were examined for their MS spectrum.
For the identification of degradation products > 10% of the original test item concentration, measurements with HPLC-UV-MS-MS, GC-MS and FT-IR were performed.
Substances, detected as degradation products, were similar for the three pH values.
The main substance in hydrolysed solutions was 1,8-Naphthalenediamine (the test substance) or a substance which shows very similar characteristics.
Several degradation products were detected with HPLC-UV-MS-MS and GC-MS.

Products greater than 10%:
Only the presumed dehydration product 1,1’-Hydrazonaphthyl-8,8’Diamine (C20H18N4) was detected with UV signal higher than 10 % of the initial test item concentration. This was proposed by mass spectroscopy, but no analytical standard was available to confirm this assignment.

Products less than 10%:
1H-Perimidine (C11H8N2) was identified by comparison with a reference standard.
2-Methyl-1H-Perimidine (C12H10N2) was also suggested by mass spectroscopy, but no analytical standard was available to confirm this assignment.

A proposed hydrolysis pathway is attached.