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Tests on hydrolysis, ready biodegradability, bioaccumulation (aquatic) and adsorption/desorption were done with aspartic acid, N,N'-[methylenebis(2-methyl-4,1-cyclohexanediyl)]bis-, 1,1',4,4'-tetraethyl ester instead of aspartic acid, N,N'-(methylenedi-4,1-cyclohexanediyl)bis-, 1,1',4,4'-tetraethyl ester with the following justification:

Aspartic acid, N,N'-[methylenebis(2-methyl-4,1-cyclohexanediyl)]bis-, 1,1',4,4'-tetraethyl ester is a structural analogue to aspartic acid, N,N'-(methylenedi-4,1-cyclohexanediyl)bis-, 1,1',4,4'-tetraethyl ester.Both substances are diethyl esters of aspartic acid linked to a dicyclohexylmethyldiamine moiety. The difference between these two substances is merely the presence of two methyl groups connected to the cyclohexane rings. This structural analogy was confirmed by the Member State responsible for the notification of both substances under the NONS regulation. The Member State decided that test results obtained for one substance can be transferred to the other substance and that testing of both substances is usually not required. This decision is in accordance with the grouping of substances and read-across approach in Annex XI, 1.5 of the REACH Regulation.

Stability (hydrolysis):

The stability of aspartic acid, N,N'-[methylenebis(2-methyl-4,1-cyclohexanediyl)]bis-, 1,1',4,4'-tetraethyl ester towards hydrolysis was determined according to the OECD-guideline 111 (Bayer Industry Services, 2006). Based on kinetic parameters, the following dissipation half-lives for a temperature of 25 °C were extrapolated based on the Arrhenius equation:

pH 4 (25 °C): t1/2: 655 h

pH 7 (25 °C): t1/2: 25.4 h

pH 9 (25 °C): t 1/2: 16.8 h

Bis-aspartic-mono-acid triethylester, bis-aspartic-di-acid diethylester, bis-aspartic-tri-acid monoethylester and bis-aspartic-tetra-acid ofaspartic acid, N,N'-[methylenebis(2 -methyl-4,1-cyclohexanediyl)]bis-,1,1',4,4'-tetraethyl esterwere determined as hydrolysis products by the means of a HPLC-MS method.

Biodegradation (in water, screening test):

Aspartic acid, N,N'-(methylenedi-4,1-cyclohexanediyl)bis-, 1,1',4,4'-tetraethyl ester is not inherently biodegradable (Currenta, 2009a). The structural analogue aspartic acid, N,N'-[methylenebis(2-methyl-4,1-cyclohexanediyl)]bis-,1,1',4,4'-tetraethyl ester is not readily biodegradable (Bayer AG, 1998a).

Adsorption / desorption:

The soil adsorption coefficient of the structural analogue aspartic acid, N,N'-[methylenebis(2-methyl-4,1-cyclohexanediyl)]bis-,1,1',4,4'-tetraethyl ester was determined according to EU-Method C.19 (HPLC-Method) yielding a logKoc between 4.2 and 5.1 (Bayer AG, 2003). The sorption coefficient was determined at pH 6 and pH 8 showing that the sorption behaviour does not depend on the prevailing pH.

According to Swann et al. (1983), the structural analogue aspartic acid, N,N'-[methylenebis(2 -methyl-4,1-cyclohexanediyl)]bis-,1,1',4,4'-tetraethyl ester has a high potential to sorb on soil.

Henry's Law Constant:

Aspartic acid, N,N'-(methylenedi-4,1-cyclohexanediyl)bis-, 1,1',4,4'-tetraethyl ester is characterised by a calculated Henry Law Constant of 0.01 Pa*m³/mol (Currenta, 2009b). According to Thomas, cited in the "Handbook of Chemical property Estimation Methods" (Lyman, 1980), the substance has to be scored as non-volatile from water.

Bioaccumulation:

A study to investigate the potential of aspartic acid, N,N'-[methylenebis(2-methyl-4,1-cyclohexanediyl)]bis-, 1,1',4,4'-tetraethyl ester to accumulate in fish yielded an uptake efficiency of 0.25 % (Currenta, 2010a). The study clearly shows that the test item has no significant potential for bioaccumulation.

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