Vinyl neononanoate

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)

GLP compliance:

yes

Specific details on test material used for the study:

Identification: VEOVA ™ Vinyl Ester Monomer 9 (Vinyl neononanoate/CAS No. 54423-67-5)
Appearance/Physical State: Clear colorless liquid
Batch: HEMV0061
Purity: As described in Section 12/1.4 of IUCLID
Storage Conditions: Room temperature in the dark

Information as provided by the supplier. The Certificate of Analysis provided by the supplier is presented as Appendix 1.

Identification: Vinyl Acetate (CAS No. 108-05-4)
Appearance/Physical State: Clear colorless liquid
Lot: A0332826
Purity: 99.9%
Expiry Date: 01 March 2016
Storage Conditions: Approximately 4 °C under nitrogen in the dark

Analytical monitoring:

yes

Details on sampling:

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 gas chromatography (GC).

Diluent A
Approximately 10.0 mg/L octane (Internal Standard) in hexane.

Samples
An aliquot (20 mL) of each sample was extracted* with an aliquot (2 ml) of Diluent A.

Sample blanks
An aliquot (20 mL) of each buffer solution (containing 1 % v/v acetonitrile) was extracted* with an aliquot (2 ml) of Diluent A.

Standards
Duplicate standard solutions of test item were prepared in Diluent A at a nominal concentration of 50 mg/L.

Standard blank
Diluent A.

Buffers:

pH 4

Citric acid 0.06 (mol dm^-3)
Sodium chloride 0.04 (mol dm^-3)
Sodium hydroxide 0.07 (mol dm^-3)

pH 7

Disodium hydrogen orthophosphate (anhydrous) 0.03 (mol dm^-3)
Potassium dihydrogen orthophosphate 0.02 (mol dm^-3)
Sodium chloride 0.02 (mol dm^-3)

pH 9

Disodium tetraborate 0.01 (mol dm^-3)
Sodium chloride 0.02 (mol dm^-3)

Details on test conditions:

Preparation of the Test Solutions
Sample solutions were prepared in stoppered glass flasks at a nominal concentration of 5 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.

Preliminary Test/Tier 1
Sample solutions at pH 4, 7 and 9 were maintained at 50.0 ± 0.5 °C for a period of 480 hours.

Tier 2
Results from the Preliminary test/Tier 1 showed it was necessary to undertake further testing at pH 4, 7 and 9, with solutions being maintained at 30.0 ± 0.5 °C and 40.0 ± 0.5 °C.

Duration:

480 h

pH:

4

Temp.:

50 °C

Initial conc. measured:

>= 2.55 - <= 2.64 mg/L

Duration:

480 h

pH:

7

Temp.:

50 °C

Initial conc. measured:

>= 2.1 - <= 2.17 mg/L

Duration:

480 h

pH:

9

Temp.:

50 °C

Initial conc. measured:

>= 2.73 - <= 2.78 mg/L

Duration:

480 h

pH:

4

Temp.:

60 °C

Initial conc. measured:

>= 3.48 - <= 3.54 mg/L

Duration:

480 h

pH:

4

Temp.:

70 °C

Initial conc. measured:

>= 3.48 - <= 3.54 mg/L

Duration:

480 h

pH:

7

Temp.:

60 °C

Initial conc. measured:

>= 3.64 - <= 3.66 mg/L

Duration:

480 h

pH:

7

Temp.:

70 °C

Initial conc. measured:

>= 3.64 - <= 3.66 mg/L

Duration:

480 h

pH:

9

Temp.:

60 °C

Initial conc. measured:

>= 4.25 - <= 4.35 mg/L

Duration:

480 h

pH:

9

Temp.:

70 °C

Initial conc. measured:

>= 4.25 - <= 4.35 mg/L

Number of replicates:

2

Positive controls:

yes

Remarks:

vinyl acetate

Statistical methods:

The linearity of the detector response with respect to concentration was assessed over the nominal concentration range of 10.8 to 108 mg/L (n = 6). The results were satisfactory with a correlation coefficient (r^2) of 0.999 being obtained.

Recovery of analysis of the sample procedure was assessed and proved acceptable for the test. At a nominal concentration of 5.0 mg/L, a mean percentage recovery of 80.5 % was obtained (range: 77.8 to 82.4 %). Concentrations have not been corrected for recovery of analysis.

Test performance:

Small peaks were occasionally observed at the approximate retention time of the test item on analysis of the matrix blank solutions. These matrix effects were only significant at very low test item concentrations. Where these matrix peaks were significant, i.e. on a par with the test item peaks, the test item concentration was considered to be “none detected”; otherwise, the matrix effects were considered to be essentially negligible and, therefore, correction for matrix blank was considered to be unnecessary.

The kinetics of the hydrolysis reaction 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.

On comparison to the hydrolysis findings for vinyl acetate (see page 92), it is noticeable that the estimated half-lives at pH 4 and 7 are comparable for both test items; whereas, the half-life for Veova 9 at pH 9 is much higher than the half-life for vinyl acetate at pH 9 (and much higher than and the half-lives for Veova 9 at pH 4 and 7). As carboxylic acid esters are known to generally hydrolyze via a base activated mechanism, it was anticipated that the Veova 9 would hydrolyze fastest at pH 9. However, it is likely that hydrolysis at pH 9 was hindered by the large carbon chain in Veova 9, leading to a much lower rate of hydrolysis.

Transformation products:

not measured

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

As the test item is an ester, it is expected that the test item will hydrolyze, via a standard ester hydrolysis reaction, to vinyl alcohol and neononanoic acids.

Key result

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

0.002 h-1

DT50:

12.3 d

Type:

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

Key result

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0.005 h-1

DT50:

6.31 d

Type:

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

Key result

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0.001 h-1

DT50:

40.9 d

Type:

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

Other kinetic parameters:

pH 4 Arrhenius Data

T (ºC) T (K) 1/T (K) kobs (hr-1) Ln kobs
50 323.15, 3.10 x 10^-3, 5.00 x 10^-3, -5.30
60 333.15, 3.00 x 10^-3, 7.86 x 10^-3, -4.85
70 343.15, 2.91 x 10^-3, 8.74 x 10^-3, -4.74

From the graph (Figure 3.10) of the above data, the rate constant and half-life at 25 °C have been estimated to be as follows:

kobs = 2.35 x 10^-3 hour-1
t½ = 294 hours
= 12.3 days

pH 7 Arrhenius Data

T (ºC) T (K) 1/T (K) kobs (hr-1) Ln kobs
50 323.15, 3.10 x 10^-3, 3.19 x 10^-2, -3.44
60 333.15, 3.00 x 10^-3, 0.123, -2.10
70 343.15, 2.91 x 10^-3, 0.139, -1.97

From the graph (Figure 3.11) of the above data, the rate constant and half-life at 25 °C have been estimated to be as follows:

kobs = 4.58 x 10-3 hour-1
t½ = 151 hours
= 6.31 days

pH 9 Arrhenius Data

T (ºC) T (K) 1/T (K) kobs (hr-1) Ln kobs
50 323.15, 3.10 x 10^-3, 4.65 x 10^-3, -5.37
60 333.15, 3.00 x 10^-3, 1.47 x 10^-2, -4.22
70 343.15, 2.91 x 10^-3, 1.88 x 10^-2, -3.97

From the graph (Figure 3.12) of the above data, the rate constant and half-life at 25 °C have been estimated to be as follows:

kobs = 7.06 x 10-4 hour-1
t½ = 982 hours
= 40.9 days

Results with reference substance:

vinyl acetate
pH Rate constant (hr-1) Estimated half-life at 25 °C
4 1.65 x 10-3 17.5 days
7 5.07 x 10-3 5.70 days
9 0.383 1.81 hours

Validity criteria fulfilled:

yes

Conclusions:

The estimated half life of vinyl neononanoate at 25 °C is 12.3 days, 6.31 days, and 40.9 days at pH 4, 7 and 9 respectively.

Description of key information

 The estimated half life of vinyl neononanoate at 25 °C is 12.3 days, 6.31 days, and 40.9 days at pH 4, 7 and 9 respectively.

Key value for chemical safety assessment

Half-life for hydrolysis:

6.31 d

at the temperature of:

25 °C