Magnesium ethanolate

Hydrolysis

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

September 2012

Reliability:

2 (reliable with restrictions)

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Principles of method if other than guideline:

In the case of hydrolysis of magnesium ethanolate in humid air a cleavage of the Mg–ethoxy bonds occurs under formation of magnesium hydroxide and evaporating ethanol.
The hydrolysis degree can be quantified by hydrolyzing the remaining ethoxy groups in water and determining the formed ethanol. The residual ethanol correlates with the content of magnesium ethanolate which did not undergo hydrolysis with the humidity of the air.

GLP compliance:

no

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products: 0, 1, 3, and 6 hrs

Details on test conditions:

The experiments were conducted in an air-conditioned laboratory at room temperature at 22 °C and relative humidity of the laboratory air of 70-90 % throughout the test.

Number of replicates:

1 per time interval at each layer

Positive controls:

yes

Remarks:

storage sample

Negative controls:

no

Statistical methods:

not applicable

Transformation products:

yes

Details on results:

The experiment with a thin layer (< 1mm) showed that a hydrolysis degree of 93.5 mol% had already been reached after one hour of exposure. After three hours, the material was nearly completely hydrolysed (99.5 mol% hydrolysis degree).

The experiment in the thicker layer (10mm) showed a lower hydrolysis degree. After one hour, only 14.7 mol% of the material was hydrolysed and after 6 hours of hydrolysis, 25.1 mol% occurred. The lower hydrolysis degree can be explained by the layer thickness of 10 mm, where the reaction starts at the top of the layer and slowly reacts further down through the 10 mm layer.

Table 1: Hydrolysis of MgOEt at different exposure times in a petri dish

Exposure in a petri dish, layer thickness < 1mm
Exposure time [h]	Hydrolysis degree [mol%]	Remarks
none	3.7	reference
1	93.5
3	99.5
6	99.6

 

Table 2: Hydrolysis of MgEth at different exposure time in a ring

 

Exposure in a ring, layer thickness 10mm
Exposure time [h]	Hydrolysis degree [mol%]	Remarks
none	3.7	reference
1	14.7
3	23.3
6	25.1

Validity criteria fulfilled:

not applicable

Conclusions:

As expected, the hydrolysis of magnesium ethanolate in air depends on the thickness of the layer.

Reference 2

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

June 2012

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

yes

Remarks:

4 time intervals instead of 6 / 2 temperatures instead of 3, 50°C omitted (Modification of section 26)

GLP compliance:

no

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

- Sampling intervals for the parent/transformation products: 1, 5, 10, and 45 min

Buffers:

- pH: 4
- Type of buffer: citric acid buffer

- pH: 7
- Type of buffer: monosodium phosphate buffer

- pH: 9
- Type of buffer: boric acid buffer

Details on test conditions:

Hydrolysis reactions were conducted at 10°C and at room temperature (21 - 23 °C) and at three pH values (4, 7, and 9).
The test concentrations were nominally intended to be 1000 mg/L, while analytical values varied between 984 and 1274 mg/L.

Number of replicates:

1 per time interval at each pH and temperature.

Positive controls:

no

Negative controls:

no

Statistical methods:

not applicable due to high reaction rate.

Preliminary study:

no

Transformation products:

yes

% Recovery:

<= 5

pH:

4

Temp.:

10 °C

Duration:

>= 5 min

% Recovery:

<= 5

pH:

4

Temp.:

23 °C

Duration:

>= 5 min

% Recovery:

<= 5

pH:

7

Temp.:

10 °C

Duration:

>= 5 min

% Recovery:

<= 5

pH:

7

Temp.:

22 °C

Duration:

>= 5 min

% Recovery:

<= 5

pH:

9

Temp.:

10 °C

Duration:

>= 5 min

% Recovery:

<= 5

pH:

9

Temp.:

21 °C

Duration:

>= 5 min

Key result

pH:

4

Temp.:

10 °C

DT50:

1 min

Type:

not specified

Key result

pH:

7

Temp.:

10 °C

DT50:

1 min

Type:

not specified

Key result

pH:

9

Temp.:

10 °C

DT50:

1 min

Type:

not specified

Details on results:

see Attachment:
In all experiments the hydrolysis of MgOEt in buffer solutions (pH4, pH7, pH9) takes place immediately. Hydrolysis rates of >= 90% within 1 minute reaction time are observed for all samples.

Validity criteria fulfilled:

not specified

Conclusions:

Magnesium ethanolate decomposes within 1 minute at pH 4; pH 7, and pH 9 at 10°C and at room temperature. 90% of the hydrolysis product ethanol could be detected after 1 minutes.

Reference 3

Endpoint:

hydrolysis

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Remarks:

The analysed substance Magnesium diethyl dicarbonate directly hydrolyses into Magnesium ethanolate (T1/2 < 1 min), which again directly hydrolyses very rapidly into carbon dioxide, ethanol and magnesium hydroxide.

Adequacy of study:

weight of evidence

Study period:

18th July 2019 - 10th August 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

The analysed substance Magnesium diethyl dicarbonate directly hydrolyses into Magnesium ethanolate (T1/2 < 1 min), which again directly hydrolyses very rapidly into carbon dioxide, ethanol and magnesium hydroxide.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

GLP compliance:

yes

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

sampling intervalls for the transformation products: 0, 1, 2, 5, 10 minutes

Buffers:

- pH: 4, Type of buffer: citric acid buffer
- pH: 7, Type of buffer: ammonium acetate buffer
- pH: 9, Type of buffer: boric acid buffer

Details on test conditions:

Hydrolysis reactions were conducted at 20°C and 50°C and at three pH values (4, 7, and 9).

Transformation products:

yes

No.:

#1

No.:

#2

Key result

pH:

4

Temp.:

20 °C

Hydrolysis rate constant:

> 0.8 min-1

DT50:

ca. 1 min

St. dev.:

6

Type:

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

Key result

pH:

7

Temp.:

20 °C

Hydrolysis rate constant:

> 0.8 min-1

DT50:

ca. 1 min

St. dev.:

9

Type:

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

Key result

pH:

9

Temp.:

20 °C

Hydrolysis rate constant:

> 0.8 min-1

DT50:

ca. 1 min

St. dev.:

10

Type:

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

Key result

pH:

4

Temp.:

50 °C

Hydrolysis rate constant:

> 0.8 min-1

DT50:

ca. 1 min

St. dev.:

6

Type:

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

Key result

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

> 0.8 min-1

DT50:

ca. 1 min

St. dev.:

9

Type:

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

Key result

pH:

9

Temp.:

50 °C

Hydrolysis rate constant:

> 0.8 min-1

DT50:

ca. 1 min

St. dev.:

10

Type:

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

Details on results:

In all experiments the hydrolysis of the test substance in buffer solutions (pH4, pH7, pH9) takes place immediately. Hydrolysis rates of >= 99% within 1 minute reaction time are observed for all samples.

Validity criteria fulfilled:

yes

Conclusions:

The test substance is hydrolysable at a very high rate (within seconds to minutes) largely irrespective of environmental conditions (relevant temperatures and pH values). Magnesium ethanolate occurs as a short-living hydrolysis product, which again directly and very rapidly hydrolyses into carbon dioxide, ethanol and magnesium hydroxide.

Description of key information

There are hydrolysis studies of magnesium ethanolate in water and air available which are the key and supporting studies. An additional OECD study is available on Magnesium diethyl dicarbonate used as weight of evidence study. Both substances decompose within minutes into the same hydrolysis products ethanol and magnesium hydroxyde.

 

Magnesium ethanolate decomposes within 1 minute at pH 4; pH 7, and pH 9 at 10°C and at room temperature in water. 90% of the hydrolysis product ethanol could be detected after 1 minute.

WATER: In contact with water, magnesium ethanolate reacts very rapidly (within minutes at 10 °C and room temperature), quantitatively and exothermically to ethanol and magnesium hydroxide: Mg⁺⁺-(O-C₂H₅)₂+ 2 H₂O ---> 2 C₂H₅OH + Mg(OH)₂.

AIR: Depending on the relative humidity in air and the surface area of magnesium ethanolate exposed to the ambient air, the substance hydrolyses rapidly in air: In free layer of powder of < 1mm, the substance was decomposed to more than 90 % at 20 °C within 1 hour. The half-life time of hydrolysis for dust of magnesium ethanolate can be assumed to be 10 - 12 min under normal ambient conditions.

 

Magnesiumdiethyl dicarbonate

The half-life of magnesium diethyl dicarbonate was determined to be T1/2 < 1 min (Hydrolysis as a Function of pH). In all experiments the hydrolysis of magnesium diethyl dicarbonate in buffer solutions (pH4, pH7, pH9) could be observed immediately. Hydrolysis rates of >= 99% within 1 minute reaction time are observed for all samples. Magnesium diethyl dicarbonate hydrolyses very rapidly via magnesium ethanolate into carbon dioxide, ethanol and magnesium hydroxide.

The hydrolysis product ethanol is readily biodegradable and the hydrolysis product magnesium hydroxide does not contain any hydrolysable functional groups. Both are natural occuring substances.

Key value for chemical safety assessment

Half-life for hydrolysis:

1 min

at the temperature of:

10 °C