Propanoic acid, 2-hydroxy-2-methyl-, 2-propen-1-yl ester

Hydrolysis

Administrative data

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Report date:

2000

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

prop-2-en-1-yl 2-hydroxy-2-methylpropanoate

EC Number:

700-908-3

Cas Number:

19444-21-4

Molecular formula:

C7H12O3

IUPAC Name:

prop-2-en-1-yl 2-hydroxy-2-methylpropanoate

Study design

Analytical monitoring:

yes

Buffers:

pH 4.0 citrate buffer 20mM sodium citrate
pH 7.0 phosphate buffer 20mM sodium phosphate
pH 9.0 borax buffer 20mM sodium tetraborate
The buffer solutions were prepared under clean room conditions, filtered through a 0.2µm membrane filter and were sterile.

Details on test conditions:

The hydrolysis solutions were stirred initially for sufficient time to ensure that the test substance had completely dissolved in the buffer solutions and that the solutions were at test temperature before the removal of the initial aliquot.
The pH values of all the hydrolysis solutions at the end of the respective tests were determined (at test temperature) and are listed along with the concentration results in the appropriate sections. The concentration of CA 2215 A in all hydrolysis solutions was less than half the solubility in water and less than 0.01M.
To exclude light from the hydrolysis system the water bath was covered in aluminium foil. As a further precautionary measure, amber volumetric flasks were used. This gave protection during the times that flasks were exposed to light, for example, for removing the aliquots.

Duration of test

Duration of test 1

Duration:

8 d

pH:

7

Temp.:

50

Initial conc. measured:

ca. 974.835 mg/L

Duration of test 2

Duration:

69 h

pH:

7

Temp.:

60

Initial conc. measured:

ca. 1 022.215 mg/L

Duration of test 3

Duration:

29.5 h

pH:

7

Temp.:

70

Initial conc. measured:

ca. 1 009.847 mg/L

Duration of test 4

Duration:

7 h

pH:

9

Temp.:

50

Initial conc. measured:

ca. 1 007.856 mg/L

Duration of test 5

Duration:

8 h

pH:

9

Temp.:

40

Initial conc. measured:

ca. 947.513 mg/L

Duration of test 6

Duration:

32 h

pH:

9

Temp.:

30

Initial conc. measured:

ca. 938.647 mg/L

Number of replicates:

2

Results and discussion

Preliminary study:

PRELIMINARY TEST:
For CA 2215 the preliminary test carried out in buffer solution 4.0 showed less than 10 % hydrolysis after 5 days. So no further work was needed for this pH value.
TEST 1:
For CA 2215 test 1 carried out at 50°C showed pseudo-first order behaviour for both the pH 7 and pH 9 buffer solutions.
TEST 2:
For CA 2215 test 2 was not necessary.
TEST 3:
For CA 2215 test 3 was carried out in the pH 7 buffer solution at 60°C and 70°C and in the pH 9 buffer solution at 30°C and 40°C. From the tests 1 and 3 the value of kobs and t1/2 are calculated.

Transformation products:

not measured

Dissipation DT50 of parent compound

Dissipation DT50 of parent compound 1

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

ca. 0.003 h-1

DT50:

ca. 214 h

Type:

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

Remarks on result:

other: correlation 0.9950

Dissipation DT50 of parent compound 2

pH:

7

Temp.:

60 °C

Hydrolysis rate constant:

ca. 0.009 h-1

DT50:

ca. 74.3 h

Type:

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

Remarks on result:

other: correlation 0.9923

Dissipation DT50 of parent compound 3

pH:

7

Temp.:

70 °C

Hydrolysis rate constant:

ca. 0.026 h-1

DT50:

ca. 26.91 h

Type:

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

Remarks on result:

other: correlation 0.9977

Dissipation DT50 of parent compound 4

pH:

9

Temp.:

50 °C

Hydrolysis rate constant:

ca. 0.203 h-1

DT50:

ca. 3.41 h

Type:

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

Remarks on result:

other: correlation 0.9970

Dissipation DT50 of parent compound 5

pH:

9

Temp.:

40 °C

Hydrolysis rate constant:

ca. 0.083 h-1

DT50:

ca. 8.4 h

Type:

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

Remarks on result:

other: correlation 0.9991

Dissipation DT50 of parent compound 6

pH:

9

Temp.:

30 °C

Hydrolysis rate constant:

ca. 0.027 h-1

DT50:

ca. 25.59 h

Type:

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

Remarks on result:

other: correlation 0.9994

Any other information on results incl. tables

Result for pH 4buffer:

The half-life time of CA 2215 in the pH 4 buffer solution was estimated from the results of the preliminary test to be greater than 1 year at 25°C and 20°C. The final pH of this experiment was determined to be 3.7. 

 

Arrhenius Fit – Extrapolation to 25°C and 20°C for pH 7:

Using Arrhenius equation, a plot of the logarithm of kobs, determined at 70°C, 60°C and 50°C versus the reciprocal of the temperature (in kelvin) was made. A straight line was obtained, the equation of which calculation using least square linear regression. 

Hydrolysis solution	Rate constant (hours^-1)		Log rate constant (hours^-1)	Temperature
	individual	average		1/K	°C
H75 H76   H73 H74   H71 H72	0.025757 0.024768   0.009327 0.009409   0.003235 0.003228	0.025262     0.009368     0.003232	-1.5975     -2.0284     -2.4906	0.002914     0.003002     0.003095	70.0     60.0     50.0

 

Substitution of 25.0°C and 20.0°C (as the reciprocal of the absolute temperature) in the Arrhenius equation yielded the log k values at these two temperatures.

Summary of results:

	25°C	20°C
kobs	0.00016801 hours^-1	0.00008752 hours^-1
t1/2	4125 hours	7919 hours
t1/2	172 days	330 days

Arrhenius Fit – Extrapolation to 25°C and 20°C for pH 9:

Using Arrhenius equation, a plot of the logarithm of kobs, determined at 50°C, 40°C and 30°C versus the reciprocal of the temperature (in kelvin) was made. 

Hydrolysis solution	Rate constant (hours^-1)		Log rate constant (hours^-1)	Temperature
	individual	average		1/K	°C
H93 H94   H95 H96   H97 H98	0.202938 0.196408   0.082545 0.083140   0.027084 0.026923	0.199673     0.082843     0.027004	-0.6997     -1.0817     -1.5686	0.003095     0.003193     0.003299	50.0     40.0     30.0

 

Substitution of 25.0°C and 20.0°C (as the reciprocal of the absolute temperature) in the Arrhenius equation yielded the log k values at these two temperatures.

Summary of results:

	25°C	20°C
kobs	0.01615033 hours^-1	0.00921470 hours^-1
t1/2	42.9 hours	75.2 hours
t1/2	1.79 days	3.13 days

 

Applicant's summary and conclusion

Conclusions:

Buffer At 20°C At 25°C
pH 3.7 > 1 year > 1 year
pH 6.6 330 days 172 days
pH 8.8 75 hours 43 hours

Executive summary:

The rate of hydrolysis of CA 2215 A has been determined at three pH values.  

The half-life times (t½) of the test substance were determined either by extrapolation of the experimental values (for buffer solutions pH 7.0 and pH 9.0) or by estimation from the preliminary test (buffer solution pH 4.0). 

Half-life times (t½)
Buffer solution	At 20°C	At 25° C
pH 3.7	> 1 year	> 1 year
pH 6.6	330 days	172 days
pH 8.8	75 hours	43 hours

 

These results have been quoted to two significant figures.