Reactionmass of octan-2-yl prop-2-enoate and octan-3-yl prop-2-enoate and octan-4-yl prop-2-enoate

Endpoint summary

Additional information

MTDID 44428 is a multi-constituent substance comprising a mixture of secondary alkyl esters of acrylic acid. The constituent isomers are the 2-, 3-, and 4-octyl acylates. Many of the properties of this substance are therefore average measurements, although isomer-specific data are sometimes available. This material has a vapor pressure of 6.4 Pa at 18°C and has water solubilities at 23.7 °C of 4.98 mg/L (2-octyl acrylate), 5.28 mg/L (3-octyl acrylate), and 4.35 mg/L (4-octyl acrylate). Some distribution to the atmosphere is expected for MTDID 44428 depending on local conditions.

MTDID 44428 is not readily biodegradable but is inherently biodegradable (not meeting specific criteria). In the abiotic control of the inherent biodegradation test, the test material could not be detected at the end of the test. In abiotic hydrolysis tests, contradictory results were obtained. In the key test, dissipation half-lives could be calculated for at 50 °C for all pH values and all isomers. Half-lives at 25 °C could be calculated for 2-octyl acrylate for all pH values, at pH 7 and 9 for 3-octyl acrylate, and only at pH 9 for 4-octyl acrylate. Half-life at 15 °C could only be determined for 2 -octyl acrylate at pH 9. Analysis of the secondary alcohol hydrolysis products could only provide a mass balance at pH 9.  At pH 4 and pH 7, concentrations of acrylate isomers as well as the corresponding secondary alcohols declined simultaneously.  In the disregarded study, disappearance of acrylate occurred much more rapidly.  Dissipation half-lives could not be calculated in any trial due to limited sampling interval. Samples were taken at zero and six hours only for 15 °C and 25 °C. Sampling at 50 °C was done until four days, but essentially all loss occurred before the first sampling time of six hours. The secondary alcohols were examined but could not be quantified in the disregarded study. It is possible that some degree adsorption occurred in the biodegradation tests, which would make the substance less available to degrading organisms. It is also possible that the hydrolysis products are not amenable to biodegradation. Secondary alcohols are expected to be converted to ketones. However, undecan-2-one was not readily biodegradable in a test done at a loading rate four times higher than its measured solubility. Nonan-2-one is easily biodegraded (test conducted at <2% of solubility limit). The registration dossier for octan-2-one contains contradictory results on ready biodegradability.

In a shake-flask study of octanol-water partition coefficient, the log Kow of MTDID 44428 was determined to be 4.8 for the 2-octyl isomer and 4.7 for the 3- and 4-octyl isomers. The constituents of MTDID 44428 therefore have partition coefficients in the range of chemicals having a potential to bioaccumulate and further evaluation was needed. No experimental studies of bioconcentration of MTDID 44428 were available, and a preliminary study showed that a BCF test under semistatic conditions would not be feasible. In a QSAR analysis using Catalogic software v.5.13.1, BCF values ranging from 9 to 10 were predicted for fish. This software establishes a baseline BCF based on log Kow and applies factors for metabolism, a conformation-based calculation of molecular size, water solubility, and presence of phenolic or acidic functional groups. This result is in agreement with well-studied metabolism of acrylate esters in mammals. It is shown that metabolism is via ester hydrolysis and is nearly complete. Acrylate esters are rapidly detoxified and eliminated.

The log adsorption coefficient (log Koc) of MTDID 44428 was found to be 2.80. This indicates that MTDID 44428 would be unlikely to bind strongly to sediment and is not expected to bind strongly to soil.