3,5-dimethylbenzoyl chloride

Hydrolysis

Administrative data

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

27 August 1992 - 4 September 1992

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted to GLP in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1993

Report date:

1993

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

yes

Remarks:

See below.

Principles of method if other than guideline:

DMBC is known to hydrolyse rapidly to DMBA (dimethyl benzoic acid) in water at room temperature. Therefore the test was performed at 25 °C and not 50 °C as recommended in the Directive for the preliminary test, in order to slow the rate of hydrolysis and attempt to obtain a direct measurement of the half-life.

In addition, the study report states that the method followed was based upon the preliminary test described in the EEC Methods for determination of ecotoxicity, Directive 84/449/EEC (OJ No. L251, 19.9.84) Part C, Method C.10. Abiotic degradation: hydrolysis as a function of pH. It is believed that this is a typographical error and should be C.7.

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

3,5-dimethylbenzoyl chloride

EC Number:

413-010-9

EC Name:

3,5-dimethylbenzoyl chloride

Cas Number:

6613-44-1

Molecular formula:

C9H9ClO

IUPAC Name:

3,5-dimethylbenzoyl chloride

Details on test material:

DMBC
Appearance: clear, colourless liquid
Storage conditions: room temperature in the dark

Radiolabelling:

no

Study design

Analytical monitoring:

yes

Details on sampling:

The test solutions were analysed within ten minutes of preparation.

Buffers:

PREPARATION OF 0.1 M BUFFER SOLUTIONS

pH 4.00 buffer:
Potassium dihydrogen citrate (11.51 g) was dissolved in distilled water (500 mL). The solution was stirred in a 50 °C water bath and the pH adjusted to 4.00 with 0.1 M sodium hydroxide solution as soon as the temperature of the buffer solution reached 50 ± 0.5 °C.

pH 7.00 buffer:
Potassium dihydrogen orthophosphate (6.81 g) was dissolved in distilled water (500 mL). The solution was stirred in a 50 °C water bath and the pH adjusted to 7.00 with 0.1 M sodium hydroxide solution as soon as the temperature of the buffer solution reached 50 ± 0.5 °C.

pH 9.00 buffer:
Potassium chloride (3.73 g) and boric acid (3.17 g) were dissolved in distilled water (500 mL). The solution was stirred in a 50 °C water bath and the pH adjusted to 9.00 with 0.1 M sodium hydroxide solution as soon as the temperature of the buffer solution reached 50 ± 0.5 °C.

Prior to the test, the buffer solutions were autoclaved at 121 °C for 15 minutes and then purged with nitrogen for 10 minutes. The solutions were then adjusted back to their stated pH values with 0.1 M sodium hydroxide and 0.1 M hydrochloric acid at 25 °C.

Details on test conditions:

PREPARATION OF SPIKING SOLUTION
DMBC (0.48698 g) was weighed into a 100 mL flask, dissolved in and made up to the mark with acetonitrile to produce a solution of 4869.8 µg/mL.

PERFORMANCE OF THE TEST
1 mL aliquots of spiking solution (4869.8 µg/mL) in acetonitrile were pipetted into three 100 mL volumetric flasks to which buffer solutions at pH 4, 7 and 9 at 25 °C were added to give a concentration of 48.698 µg/mL DMBC. These solutions were subsequently diluted by a factor of ten in mobile phase prior to injection.
Buffer was similarly diluted with mobile phase to act as a blank.

CALIBRATION STANDARDS
DMBC (0.50998 g) was added to a 100 mL volumetric flask dissolved in and made up to the mark with acetonitrile. A 2 mL aliquot of this solution was pipetted into a 100 mL volumetric flask and made up to the mark with distilled water to give a solution of concentration 102.00 µg/mL DMBC equivalent to 90.839 µg/mL DMBA after hydrolysis. This solution was subsequently diluted to yield a range of standards between 10.901 µg/mL DMBA and 3.6336 µg/mL DMBA. The use of DMBC as the calibration standard is considered appropriate since DMBC has been found to hydrolyse completely to DMBA in aqueous media. No peak was observed for DMBC in the chromatography for the calibration standards (retention time ca. 2 - 8 minutes).

Duration of test

Duration of test 1

Duration:

10 min

pH:

4

Temp.:

25 °C

Initial conc. measured:

38.721 other: µg/mL (as DMBA)

Duration of test 2

Duration:

10 min

pH:

7

Temp.:

25 °C

Initial conc. measured:

39.107 other: µg/mL (as DMBA)

Duration of test 3

Duration:

10 min

pH:

9

Temp.:

25 °C

Initial conc. measured:

42.694 other: µg/mL (as DMBA)

Statistical methods:

CALCULATION
The peak response of DMBA in each calibration standard was measured and calibration curves were constructed by linear regression of standard response versus standard concentration. The response of the peak observed at the characteristic retention time of DMBA in the samples was measured and the concentration was determined using the equation:

Concentration (C) (µg/mL) = [(Y - I) / S] x F

where Y = peak response
I = intercept derived from linear regression of calibration data
S = slope derived from linear regression of calibration data
F = dilution factor (10)

The conversion of DMBC concentration to DMBA concentration was achieved by the multiplication of a factor derived so:
Relative molecular mass DMBA / Relative molecular mass DMBC = 150.1768 / 168.6225 = 0.89061

Therefore concentration of DMBA in the test solutions assuming complete hydrolysis was 43.371 µg/mL.

Results and discussion

Transformation products:

yes

Identity of transformation products

No.:

#1

Reference

Reference substance name:

Unnamed

IUPAC name:

3,5-dimethylbenzoic acid

Inventory number:

InventoryMultipleMappingImpl [inventoryEntryValue=EC 207-876-5]

CAS number:

499-06-9

Identity:

3,5-dimethylbenzoic_acid

Identity:

Benzoic acid, 3,5-dimethyl-

Molecular formula:

C9H10O2

Molecular weight:

150.174

SMILES notation:

Cc1cc(C)cc(c1)C(=O)O

InChl:

InChI=1/C9H10O2/c1-6-3-7(2)5-8(4-6)9(10)11/h3-5H,1-2H3,(H,10,11)

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

DMBC hydrolysed to DMBA (dimethyl benzoic acid) on contact with water at room temperature.

Dissipation DT50 of parent compound

Key result

pH:

6

Temp.:

25 °C

DT50:

<= 10 min

Details on results:

Calibration data provided a slope of 34694, an intercept of 8904.7 and correlation coefficient of 0.99857 showing a linear relationship between detector response and concentration.

The blank buffers exhibited no peaks at the characteristic retention times of DMBC and DMBA showing that the method is free of interferences.

The test chromatograms showed complete hydrolysis to dimethyl benzoic acid. An occasional small peak was observed at the retention time of DMBC both on calibration and sample chromatograms but was not considered to be significant.

The DMBA and DMBC retention times have been verified by use of analytical grade standards and were found to be ca. 5.1 minutes and ca. 2.8 minutes respectively.

Full hydrolysis occurs within 10 minutes at 25 °C, therefore, the half-life of DMBC is less than 1 day at 25 °C in pH 4, 7 and 9 in aqueous buffers.

Any other information on results incl. tables

Table 1 Calibration Standards (Concentration expressed as µg/mL DMBA - Hydrolysis product of DMBC)

Concentration of DMBA (µg/mL)	Integrated Peak Area
3.636 5.4503 7.2671 9.0839 10.901	141242 197565 256896 320759 385909	194638	130579 200962 259976 332694
Correlation Coefficient Slope Intercept	0.99857 34694 8904.7

 

Table 2 Analytical Data: DMBA (hydrolysis product of DMBC)

Time Point	pH	Peak Area	Concentration of DMBA in Buffer Solution (µg/mL)	Concentration of DMBA (assuming complete hydrolysis, µg/mL)	% Recovery
0 hours	4 7 9	143243 144583 157028	38.721 39.107 42.694	43.371 43.371 43.371	89.3 90.2 98.4

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

Full hydrolysis occurs within 10 minutes at 25 °C, therefore the half-life of DMBC is less than 1 day at 25 °C in pH 4, 7 and 9 in aqueous buffers.

Executive summary:

A study was performed to assess the abiotic degradation of DMBC. The method followed was based upon the preliminary test described in the EEC Methods for determination of ecotoxicity, Directive 84/449/EEC (OJ No. L251, 19.9.84) Part C, Method C.7. Abiotic degradation: hydrolysis as a function of pH.

 

The starting concentration was 48.698 µg/mL, a concentration that represented less than 0.01 M and less than half the saturated concentration of DMBC in each of the buffer solutions. The 10 minutes represents the preparation time plus the analysis time by HPLC. A solution thus prepared and injected, showed a large peak at ca. 5.1 minutes, the characteristic DMBA retention time and no or negligible peak at the characteristic retention time of DMBC (ca. 2.8 minutes).

DMBC was completely hydrolysed to DMBA in less than 10 minutes at 25 °C in aqueous solution at pH 4, 7 and 9.