Magnesium ethanolate

Adsorption / desorption

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

adsorption / desorption: screening

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance and its relevant degradation products decompose rapidly

Justification for type of information:

Magnesium ethanolate hydrolyses very rapidly in contact with moisture or water. Based on the available data it can be considered that magnesium ethanolate and its hydrolysis products ethanol and magnesium hydroxide have a low potential for adsorption to soil. The degradation products ethanol and magnesium hydroxide are natural occuring substances, magnesium ethanolate and ethanol are readily biodegradable.

Reference 2

Endpoint:

adsorption / desorption

Remarks:

adsorption

Type of information:

calculation (if not (Q)SAR)

Remarks:

KOCWIN v. 2.00 (US EPA 2010)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

accepted calculation method

Remarks:

KOCWIN v. 2.00 (US EPA 2010)

Qualifier:

no guideline followed

Guideline:

other: calculation method, POCWIN v. 2.00, US EPA 2010

Principles of method if other than guideline:

The Soil Adsorption Coefficient Program (KOCWIN) estimates the soil adsorption coeffiecient (Koc) of organic compounds.  Koc can be defined as "the ratio of the amount of chemical adsorbed per unit weight of organic carbon (oc) in the soil or sediment to the concentration of the chemical in solution at equilibrium" (Lyman, 1990); it is represented by the following equation (Lyman, 1990):

 Koc =  (ug adsorbed/g organic carbon) / (ug/mL solution)

The units of Koc are typically expressed as either L/kg or mL/g.

Koc provides an indication of the extent to which a chemical partitions between solid and solution phases in soil, or between water and sediment in aquatic ecosystems.  Estimated values of Koc are often used in environmental fate assessment because measurement of Koc is expensive.  Traditional estimation methods rely upon the octanol/water partition coefficient or related parameters, but the first-order molecular connectivity index (MCI) has been used successfully to predict Koc values for hydrophobic organic compounds (Sabljic, 1984, 1987; Bahnick and Doucette, 1988).  The original KOCWIN program (PCKOC) used MCI and a series of group contribution factors to predict Koc (Meylan et al., 1992).  This group contribution method was shown to outperform traditional estimation methods based on octanol/water partition coefficients and water solubility.

Since the introduction of the original PCKOC program in 1992, the number of available experimental Koc values has grown significantly.  Using an expanded experimental dataset and the original PCKOC methodology, the QSAR equations were re-regressed to derive updated coefficient values.  In addition, several new group contribution factors (correction factors) were added to improve estimation accuracy.  Also, the updated KOCWIN program includes a separate Koc estimate based upon Log Kow (rather than MCI).  A brief description of the estimation methodology and accuracy is presented in the Methodology section and Accuracy section of this help file.

KOCWIN requires only a chemical structure to make these predictions.  Structures are entered into KOCWIN by SMILES (Simplified Molecular Input Line Entry System) notations.  A discussion of the encoding rules for SMILES notation can be found in the document "A Brief Description of SMILES Notation".  

The following journal article explains the MCI prediction methodology and its use:

(1) Meylan, W., P.H. Howard and R.S. Boethling, "Molecular Topology/Fragment Contribution Method for Predicting Soil Sorption Coefficients", Environ. Sci. Technol. 26: 1560-7 (1992).

Journal abstract:

"The first-order molecular connectivity index (MCI) has been successfully used to predict soil sorption coefficients (Koc) for nonpolar organics, but extension of the model to polar compounds has been problematic.  To address this, we developed a new estimation method based on MCI and series of statistically derived fragment contribution factors for polar compounds. After developing an extensive database of measured Koc values, we divided the dataset into a training set of 189 chemicals and an independent validation set of 205 chemicals.  Two linear regressions were then performed.  First, measured log Koc values for nonpolar compounds in the training set were correlated with MCI.  The second regression was developed by using the deviations between measured log Koc and the log Koc estimated with the nonpolar equation and the number of certain structural fragments in the polar compounds.  The final equation for predicting log Koc accounts for 96% and 86% of the variation in the measured values for the training and validation sets, respectively.  Results also show that the model outperforms and covers a wider range of chemical structures than do models based on octanol-water partition coefficients (Kow) or water solubility."

 

GLP compliance:

no

Type of method:

other: calculated

Media:

soil

Type:

Koc

Value:

2.2 L/kg

Remarks on result:

other: estimated from logKow

Executive summary:

Magnesium ethanolate hydrolyses within minutes to magnesium hydroxide and ethanol. According to an acceptable calculation method (KOWWIN v. 2 of the US EPA (2010), the hydrolysis product ethanol has a low potential for adsorption to soil.

Description of key information

Magnesium ethanolate hydrolyses very rapidly in contact with moisture or water.  Based on the available data it can be considered that magnesium ethanolate and its hydrolysis products ethanol and magnesium hydroxide have a low potential for adsorption to soil. The degradation products ethanol and magnesium hydroxide are natural occuring substances, magnesium ethanolate and ethanol are readily biodegradable.