Benzoic acid, 3-amino-5-[[[2,3-bis(acetyloxy)propyl]amino]carbonyl]-2,4,6-triiodo-

Hydrolysis

Administrative data

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2001-12-17 to 2002-03-13

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2002

Report date:

2002

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

rac-5-Amino-N-(2,3-diacetoxypropyl)-2,4,6-triiodoisophthalamic acid

EC Number:

602-891-7

Cas Number:

122731-59-3

Molecular formula:

C15 H15 I3 N2 O7

IUPAC Name:

rac-5-Amino-N-(2,3-diacetoxypropyl)-2,4,6-triiodoisophthalamic acid

Radiolabelling:

no

Study design

Analytical monitoring:

yes

Details on sampling:

At each sampling time two vials from each of the hydrolysis solutions at pH 4, 7 and 9 were removed from the thermostatic bath and aliquots of each vessel were analyzed by HPLC or, in case of the experiment at pH 9, 25 °C, the vials were directly analyzed. The sampling times and the measured concentrations of ZK 91248 are listed in Tables 1 – 2 and 5.

Buffers:

Buffer solutions
-0.05 M acetate buffer solution pH 4
0.657 g 0.008 mol sodium acetate p.a. Merck Art. 106268 (M = 82.03 g/mol) and 2.4 mL =0.042 mol acetic acid 100 % p.a. Merck Art. 100063 E (M = 60.05 g/mol, density = 1.05 g/mL) were dissolved to 1000 mL with double distilled water. The pH value was adjusted to 4 by adding acetic acid (see above).
-0.05 M phosphate buffer solution pH 7
4.34 g=0.031 mol disodium hydrogen phosphate Merck Art. 106566 (M = 141.96 g/mol) and 2.64 g=0.019 mol potassium dihydrogen phosphate Merck Art. 105108 (M = 136.09 g/mol) were dissolved to 1000 mL with double distilled water. The pH value was adjusted to 7 by adding 0.1 M sodium hydroxide solution (Titrisol Merck Art. 109959)
-0.05 M borate buffer solution pH 9
2.52 g=0.0125 mol disodium tetraborate Merck Art. 106309 (M = 201.22 g/mol) and 46 mL=0.0046 mol hydrochloric acid Titrisol Merck Art. 109973 (0.1 M) were dissolved to 1000 mL with double distilled water. The pH value was adjusted to 9.00 by adding 0.1 M sodium hydroxide solution (Titrisol Merck Art. 109959).

Details on test conditions:

Aliquots of the test solutions were filled into sterilized 5 ml autosampler vials which were tightly closed with screw caps. For the experiments at 50 and 80 °C, the vials were incubated in athermostatic water bath at the corresponding test temperature. The temperature was kept constant within ± 0.1 °C. The experiment at 25 °C was conducted in the thermostated cabinet of anautosampler. Prior to incubation the initial concentration of ZK 91248 was measured on the test solutions of pH 4, 7 and 9. During the incubation of the test solutions in the thermostatic water bath possible photolytic degradation of the test substance was prevented by exclusion of light from the hydrolysis solutions by using a thermostatic bath made of stainless steel with a metal cover.

Duration of test

Duration of test 1

Duration:

92 h

pH:

9

Temp.:

25

Initial conc. measured:

9.99 mg/L

Duration of test 2

Duration:

25 h

pH:

7

Temp.:

80

Initial conc. measured:

10.34 mg/L

Duration of test 3

Duration:

360 h

pH:

7

Temp.:

50

Initial conc. measured:

10.68 mg/L

Duration of test 4

Duration:

360 h

pH:

4

Temp.:

50

Initial conc. measured:

11.12 mg/L

Results and discussion

Preliminary study:

yes

Transformation products:

yes

Identity of transformation products

No.:

#1

Reference

Reference substance name:

Unnamed

IUPAC name:

rac-5-Amino-N-(2,3-dihydroxypropyl)-2,4,6-triiodoisophthalamic acid

Inventory number:

InventoryMultipleMappingImpl [inventoryEntryValue=EC 601-093-6]

CAS number:

111453-32-8

Molecular formula:

C11 H11 I3 N2 O5

Molecular weight:

631.917

SMILES notation:

C(C(CO)O)NC(=O)C1=C(C(=C(C(=C1I)N)I)C(=O)O)I

InChl:

InChI=1S/C11H11I3N2O5/c12-6-4(10(19)16-1-3(18)2-17)7(13)9(15)8(14)5(6)11(20)21/h3,17-18H,1-2,15H2,(H,16,19)(H,20,21)

Dissipation DT50 of parent compound

Dissipation DT50 of parent compound 1

pH:

4

Temp.:

25 °C

DT50:

> 1 yr

Remarks on result:

other: stable according to pretest

Dissipation DT50 of parent compound 2

Key result

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0 h-1

DT50:

144 d

Remarks on result:

other: Arrhenius extrapolation

Dissipation DT50 of parent compound 3

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0.013 h-1

DT50:

52 h

Any other information on results incl. tables

Table 1:  Sampling times and measured concentrations of the test compound in the hydrolysis solutions at pH 4, 50 °C

time [hours]	concentration (mean) [mg/l]	standard deviation of mean concen-tration [mg/l]	concentration (mean) in % of initial concentration
0.0 18.5 24.5 48.0 72.0 92.3 165.4 191.1 216.2 259.3 359.7	11.12 10.80 11.22 10.92 10.89 10.97 11.16 10.58 10.74 10.68 10.47	0.09 0.07 0.58 0.04 0.07 0.12 0.13 0.11 0.16 0.06 0.04	100.0 97.1 100.9 98.2 97.9 98.7 100.4 95.1 96.6 96.0 94.2

Table 2:  Sampling times and measured concentrations of the test compound in the hydrolysis solutions at pH 7, 50 °C

time [hours]	concentration (mean) [mg/l]	standard deviation of mean concen-tration [mg/l]	concentration (mean) in % of initial concentration
0.0 18.5 24.5 48.0 72.0 92.3 165.4 191.1 216.2 259.3 359.7	10.68 9.69 9.46 8.22 7.75 6.99 5.15 4.40 3.61 3.42 2.14	0.02 0.08 0.03 0.39 0.09 0.07 0.10 0.02 0.06 0.05 0.01	100.0 90.7 88.5 76.9 72.6 65.5 48.2 41.2 33.8 32.0 20.0

Table 3:  Sampling times and measured concentrations of the test compund in the hydrolysis solutions at H 7, 80 °C

solution	time [h]	concentration (mean) [mg/l]	concentration (mean) in % of initial concentration
pH 7/1	0 0.9 2.0 3.1 5.4 8.0 15.5 24.5	10.34 9.65 8.76 7.64 5.49 4.67 2.24 0.89	100.0 93.3 84.7 73.9 53.0 45.2 21.6 8.6
pH 7/2	0 1.5 2.0 3.0 5.4 8.0 15.5 24.5	9.62 8.43 8.11 7.11 5.09 4.37 2.11 0.77	100.0 87.6 84.3 73.9 52.9 45.5 21.9 8.0

Table 4:  Sampling times and measured concentrations of the test compounds in the hydrolysis solutions at pH 9, 25 °C

time [h]	concentration (mean) [mg/l]	concentration (mean) in % of initial concentration
0 1.9 3.5 5.2 6.8 8.5 10.2 11.9 47.6 50.1 90.1 91.8	9.99 9.74 9.53 9.31 9.16 8.96 8.75 8.58 5.29 5.10 2.93 3.03	100.0 97.5 95.3 93.2 91.7 89.7 87.6 85.9 52.9 51.0 29.3 30.3

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Executive summary:

The pretest at pH 4, 50°C indicated less than 10% decay and therefore, according to the guideline, the compound is to be considered to be stable at 25°C. At pH 7, 50°C more than 10% were degraded and therefore further experiments at 80°C were performed. The half-lives found in the experiments at elevated temperatures were extrapolated to 25°C with use of the Arrhenius equation. The hydrolysis at pH 9 was directly monitored at 25°C.

 

The rate constants and half-lives at 25 °C are

 

pH	k   [h^-1]	95 % confidence intervals for k [h^-1]	half-life	95 % confidence intervals for half-life
4	-	-	stable*	-
7	2.001 · 10^-4	1.856 · 10^-4 - 2.146· 10^-4	144 d	135 ¿ 156 d
9	1.334 · 10^-2	1.316 · 10^-2 - 1.353· 10^-2	52.0 h	51.2 ¿ 52.7 h

* criterion according to EC testing guideline C.7: half-life > 1 year at 25 °C

 

The hydrolysis rates increase with pH, indicating a base-catalized hydrolysis.

wo ester functions are present in the molecule leading to three possible hydrolysis products by cleavage of one of the ester functions or of both of them. Two of the products can be identified by peaks at 1.3 and 2.3 min in the chromatograms of the hydrolysis solutions at pH 7.

The peak at 2.3 min is an intermediate product (product of single ester cleavage) since its peak area only increases until one half-life and then decreases. The peak at 1.3 min appears to be the final hydrolysis product obtained by hydrolysis of both ester functions.