1,1'-dithiobis[hexahydro-2H-azepin-2-one]

Endpoint summary

Additional information

Stability

The phototransformation in air of the substance was determined with the help of the computer program AOPWIN v1.92 (Chemservice S.A., 2011). An atmospheric half-life of 27.43 minutes was estimated and neither an ozone reaction nor any nitrate radical reaction is important for the chemical. Hydrolysis was experimentally investigated at 50 °C according to OECD Guideline 111 (Neuland, 2012). At pH 4 and 7, the substance can be regarded as hydrolytically stable. A half-life of 21.2 h and a rate constant of 9.09E-6 s-1 (0.00000909 s-1) were determined at pH 9.Caprolactam (Hexyhydro-2H-azepin-2 -one, CAS 105 -60 -2) was determined as transformation product by Mass Spectrometry (MS). Amides were detected by HYDROWIN v1.00 in the molecule as hydrolysable substance class (Chemservice S.A., 2011). With the exception of a few halogenated acetamides, most amides hydrolyse to acids extremely slow with a half-life in centuries.

Biodegradation

Three different experimental results as well as a QSAR prediction are available regarding biodegradation in water for the test substance. Under the strict terms of OECD Guideline 301B (Mead, 2001) as well as under OECD Guideline 301F (Richter, 2011), the test substance is considered as "not readily biodegradable" since it attained only 36 % and 18 % degradation after 28 days, respectively. The prediction with BIOWIN v4.10 supports these results, since the substance is not expected to biodegrade fast neither under aerobic nor under anaerobic conditions (Chemservice S.A., 2011). According to Toxtree (v2.1.0) the chemical was assigned to the class II - persistent chemical (Chemservice S.A., 2011). Furthermore, the substance cannot be considered as inherently biodegradable as well according to OECD Guideline 302 C, since only 56 % degradation was measured after 28 days in this experiment (Richter, 2011). However, according to the German Umweltbundesamt (UBA) the test substance is considered as “Partially Biodegradable". In conclusion, the substance is not persistent in the environment and since no exposure is intended during the different life cycle stages, no further testing regarding biodegradation in water and sediment or soil is triggered.

Bioaccumulation

Aquatic bioaccumulation is predicted with the help of the computer program BCFBAF v3.00 (Chemservice S.A., 2011). Using the regression-based estimate, a Bioconcentration Factor (BCF) of 14.2 L/kg wet-wt was calculated. The Arnot-Gobas method resulted in an aquatic BCF of 19.9 L/kg wet-wt. Considering these results, a bioaccumulation in biota is unlikely. A terrestrial bioaccumulation study is not triggered for a registration of a tonnage band of 100 - 1000 tons/year according to REACH Regulation 1907/2006 EG.

Transport and distribution

A scientifically accepted calculation method (KOCWIN v2.00) was used by Chemservice S.A. (2011) to predict the adsorption coefficient of the test substance. The Salbjic molecular connectivity (MCI) method resulted in a Koc value of 491.1 L/kg, whereas the traditional method gives a value of 26.06 L/kg. The MCI method is taken more seriously into account since it includes improved correction factors.

Henry´s law states that the solubility of a gas in a liquid solution at a constant temperature will be proportional to the partial pressure of the gas which is above the solution (Henry, 1803). This information is not mandatory for a registration under REACH in a tonnage band of 100 - 1000 tons/year. However, the Henry´s Law Constant can be predicted with HENRYWIN v3.20 (Chemservice S.A., 2011), resulting in a value of 0.0000000237 Pa*m³/mol (2.37 E-008 Pa*m³/mol) at an ambient temperature of 25 °C. This value is used in the chemical safety assessment for the substance and for the derivation of the PNECsoil by means of the equilibrium assumption.