tert-butyl methacrylate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2006-10-03 to 2006-10-24

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)

Version / remarks:

2004

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

The sample solution vessels were removed from the waterbath at various times and the pH of each solution was recorded.
The concentration of each sample solution was determined by high performance liquid chromatography (HPLC).

SAMPLES
Duplicate aliquots (A and B) of the sample solutions were diluted by a factor of 4 using methanol.

Buffers:

see table 1
The buffer solutions were filtered (0.2 µm), ultrasonicated and degassed with nitrogen.

Estimation method (if used):

From the graph of log10 concentration (g/l) versus time, the rate constant was calculated using the following equation:
k_obs =-slope x 2.303
and the half-life was obtained from the rate constant as following:
t1/2= 0.693/ k_obs
(k_obs =rate constant (1/h); t1/2 = half-life (h))
By plotting the natural logarithm of the rate constants against the reciprocal of the temperature (K), the rate constant and half-lives at 25°C were obtained by extrapolation.

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks used: stoppered glass flasks
- Measures taken to avoid photolytic effects: The solutions were shielded from light whilst maintained at the test temperature.

TEST MEDIUM
- Identity and concentration of co-solvent: 1% co-solvent of acetonitrile used to aid solubility

Duration:

77 h

pH:

4

Temp.:

60

Initial conc. measured:

ca. 50 mg/L

Duration:

48 h

pH:

4

Temp.:

70

Initial conc. measured:

ca. 50 mg/L

Duration:

77 h

pH:

7

Temp.:

60

Initial conc. measured:

ca. 50 mg/L

Duration:

48 h

pH:

7

Temp.:

70

Initial conc. measured:

ca. 50 mg/L

Duration:

77 h

pH:

9

Temp.:

60

Initial conc. measured:

ca. 50 mg/L

Duration:

48 h

pH:

9

Temp.:

70

Initial conc. measured:

ca. 50 mg/L

Number of replicates:

2

Positive controls:

no

Negative controls:

yes

Remarks:

control standards

Preliminary study:

Based on the results of the preliminary test at 50 degree C the half-life t1/2 of TBMA was found to be 109 h at pH 4, 114 h at pH 7 and 107 h at pH 9.

Transformation products:

yes

No.:

#1

No.:

#2

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

The decomposition of the test substance tert-butyl methacrylate (TBMA) was monitored by HPLC-UV. The resulting hydrolysis products are methacrylic acid and t-butanol.

pH:

1.2

Temp.:

37 °C

Hydrolysis rate constant:

0

DT50:

5.48 h

Type:

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

pH:

4

Temp.:

25 °C

Hydrolysis rate constant:

0

DT50:

122 d

Type:

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

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0 s-1

DT50:

135 d

Type:

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

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0 s-1

DT50:

133 d

Type:

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

Validity criteria fulfilled:

yes

Conclusions:

The test material undergoes hydrolysis with a half life from 122 d at pH 4 and 25 °C to 133 d at pH 9 under the same test conditions. As hydrolysis products methacrylic acid (2-methyl-2-propenoic acid) and t-butanol (2-methyl-2-propanol) were identified.

Executive summary:

An experimental study according to the guideline OECD 111 (Hydrolyses as function of pH) under GLP standards was conducted to assess the potential for abiotic hydrolytic transformation of the test material in aquatic systems at pH 4,7 and 9. Therefore, 50 mg/l (nominal concentration) of the test item were incubated at the different pH values and a temperature of 50, 60  and 70°C, the concentrations were determined by HPLC. Graphs of the common logarithm of the concentration (g/1) versus time (hours) were plotted and the rate constant and half-life was calculated from this. By plotting the natural logarithm of the rate constants against the reciprocal of the temperature (K), the rate constant and half-lives at 25°C were obtained by extrapolation.

Linearity of the detector response with respect to concentration were assessed over the nominal concentration range of 0 to 100 mg/1 for pH 4, 7 and 9. These were satisfactory with correlation coefficients of 1.000 being obtained and therefore confirm the validity of the results.

The test material undergoes hydrolysis with following half-life and rate constants (see table 2). As hydrolysis products of the test material methacrylic acid (2-methyl-2-propenoic acid) and t-butanol (2-methyl-2-propanol) were identified.

Table 2: Rate constants and estimated half-lives of the test material for the different pH values

pH	Rate constant (s^-1)	Estimated half-life
1.2	3.52 X 10^-5	5.48 hours at 37°C
4	6.55 X 10^-8	I22 days at 25°C
7	5.96 X 10^-8	135 days at 25°C
9	6.02 X 10^-8	133 days at 25°C

Description of key information

In contact with water tert-butyl methacrylate shows slow hydrolysis.
Calculated half-life at pH 7 and 25 °C: 135 d

Key value for chemical safety assessment

Half-life for hydrolysis:

135 d

at the temperature of:

25 °C

Additional information

Based on the results obtained in an experimental study following OECD guideline 111 (2004), tert-butyl methacrylate (TMBA) hydrolysed slowly in contact with water at pH 4, 7 and 9 at temperatures of 50°C, 60°C and 70°C. The half-life at pH 7 and 25 °C was determined to be 135 d. As hydrolysis products methacrylic acid and t-butanol were identified (Safepharm laboratories, 2007).

In a supporting study in section 5.2.1 the ready biodegradbility of methacrylic acid in water was confirmed in an experimental study. After 28 days 86 % were degraded in an OECD 301D guideline study and the 10 day window criteria was met (Douglas-Huntingdon, 1992). In QSAR calculations with OASIS Catalogic v.5.14.1.5 the ready biodegradability of t-butanol was assesed. The model predicted a biodegrdation of 72 +- 16 % after 28 days.

 

In addition, Q(SAR) data using SRC HYDROWIN v2.00 were used as supporting data, indicating even slower hydrolysation of TBMA in contact with water (calculated half-life at pH 7 and 25 °C: 179 years; at pH 8 and 25 °C: 17.9 years) (BASF SE, 2009).