2-methylbutyl acrylate

Endpoint summary

Additional information

Stability (abiotic transformation) endpoints generally consist of hydrolytic and phototransformation reactions. Hydrolysis is not expected to contribute significantly to the fate of 2-MBA. The related compound n-butyl acrylate (n-BA) has an abiotic hydrolytic half-life of 1100 days at pH 7, 25 °C. 2-MBA is expected to be somewhat less hydrolytically active than n-BA because of the methyl branch adjacent to the ester bond. In addition, 2-MBA and n-BA are readily biodegradable. 2-MBA would be biodegraded in non-sterile aquatic and terrestrial systems well before abiotic hydrolysis would occur. We have proposed adaptation (omission) of the data requirement for hydrolysis for 2-MBA, owing to its ready biodegradability. It is important that phototransformation of 2-MBA in air be considered. 2-MBA is volatile (vapour pressure, 1.7 hPa at 20 °C, Henry's Law constant, 96 Pa*m3/mol at 23.1 °C) and may partition to the atmospheric compartment. A DT50 of 1.04 days for reaction of 2-MBA with hydroxyl radicals was estimated using AOPWIN v.1.92. This software relies on a structure fragment approach to calculating a defined endpoint, the rate constant for reaction of a substance with hydroxyl radical. The training set for this software contains 667 individual chemicals, from which a variety of structural fragments were defined. Partial rate constants for each individual fragment are weighted by a scaling factor and summed to arrive at an overall rate constant for the substance in question. From the log-log plot of derived and experimental hydroxyl radical reaction rate constants for training set chemicals, the correlation coefficient (r2) is 0.963, the standard deviation is 0.218, and the absolute mean error is 0.127. The model is generally valid and applicable for substances which are completely described by the structural fragments developed for the software. 2-MBA contains only structural fragments that are defined within the software, and further the training set itself contains acrylates and methacrylates. 2-MBA is therefore within the applicability domain of the software.