2-methylbutyl acrylate

Biodegradation in water: screening tests

Description of key information

60% BOD/ThOD after 11 days in an OECD 301D test

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

2-MBA was tested in a closed-bottle assay due to its volatility. It was 50% degraded by day 7 and 60.0% degraded by day 11. That further biodegradation was not seen is suspected to be due to volatility of the test substance, the distinctive odor of which could not be detected even in abiotic samples at the end of the study period. The ready biodegradability of 2-MBA is supported by data from two analogous compounds. n-Butyl acrylate (n-BA) differs from 2-MBA by the latter's additional methyl branch adjacent to the ester moiety on the alcoholic side of the molecule. Molecular weight, hydrophobicity and vapor pressure are similar between 2-MBA and n-BA. n-BA is readily biodegradable, showing 80-90% biodegradation in an OECD 310 assay. The OECD 310 assay was developed specifically to test ready biodegradation of highly volatile test compounds. The entirely linear structure of n-BA is expected to be somewhat more amenable to esterase activity and beta-oxidation than the 2-methyl branched structure of 2-MBA. The second analogous compound, isooctyl acrylate (IOA), is a UVCB substance possessing a variety of branched structures in its alcoholic domain. The alcoholic domain consists mostly (>94.0%) of C8 iso-alcohols with smaller amounts of C7 and C9. IOA is more hydrophobic, less water soluble, and of higher molecular weight than 2-MBA, implying a molecule less amenable to biodegradation. The mixed branching and lengths of the alcohol units complicates biodegradation relative to 2-MBA as the enzymatic systems must be able to process a wider variety of starting materials and intermediates. Read-across from IOA provides a conservative assessment of 2-MBA's biodegradation potential. Nevertheless, IOA was 93-95% biodegraded in a 28-day OECD 301D bioassay. The increased biodegradation of IOA relative to 2-MBA may be due in part to the lower vapor pressure of IOA, leading to decreased volatilization losses from test bottles. Based on the available data, it can be concluded that 2-MBA is readily biodegradable.

Data matrix – Analog approach
	Target substance	Source substance (1)	Source substance (2)
CHEMICAL NAME	2-methylbutyl acrylate	n-butyl acrylate	Isooctyl acrylate
CAS#	44914-03-6	141-32-2	29590-42-9
Molecular formula	C8H14O2	C7H12O2	C11H20O2 (on average)
Molecular Weight	142.2	128.2	184.3 (on average)
PHYSICO-CHEMICAL DATA
Melting Point	Experimental: ≤ -75 °C	Not available	Experimental: < -90 °C at 1004 hPa
Boiling Point	Experimental: 161.7 °C at 1013hPa	Experimental: 147 °C at 1013hPa	Experimental: 196.8 °C at 1016 hPa
Density	Experimental: 0.8886 g/cm3 at 25 °C	Experimental: 0.9 g/cm3 at 20.0 °C	Experimental: 0.885 g/cm3 at 20.0 °C
Vapour Pressure	Experimental: 1.7 hPa at 20°C	Experimental: 5 hPa at 22.2°C	Experimental: 1 hPa at 20 °C
Partition Coefficient (log KOW)	Experimental: 2.9	Experimental: 2.38 (at 25°C)	Experimental: 4.5 - 4.7
Water Solubility	Experimental: 316 mg/L at 23 °C	Not available	Experimental: 12.44 mg/L at 23.1 °C
ENVIRONMENTAL FATE and PATHWAYS
Photodegradation	QSAR: DT50 1.04 d (AOPWIN v1.92)	Not determined	QSAR: 17.4 - 21.4 h (AOPWIN v.1.92)
Stability in Water	Adaptation, readily biodegradable	Experimental: DT50, 1100 day at pH 7, 25 °C (40CFR796.3500)	Adaptation, readily biodegradable
Aerobic Biodegradation	Experimental: 60% after 11 days (OECD 301D)	Experimental: 80 - 90% after 28 days (OECD 310)	Experimental: 93-95% after 28 days (OECD 301D)
Bioconcentration	Not bioaccumulative (Low log Kow, extensive metabolism)	Not bioaccumulative (Low log Kow, extensive metabolism)	Not bioaccumulative (Extensive metabolism)
Transport and Distribution	Koc 263 – 302 (Calculated by TGD method)	Experimental: Koc 40-148 (EPA OTS 796.2750)	Experimental: Koc 650-3900 (OECD117)
Henry's Law constant	Experimental: 96 Pa*m3/mol at 23.1 °C	Not determined	Experimental: 1780 Pa*m3/mol at 23.1 °C
ENVIRONMENTAL TOXICITY
Toxicity to Microorganisms (activated sludge respiration)	Experimental: 3-hour EC50 >1000 mg/L (OECD 209)	Experimental: 3d EC50 >150 mg/L (ASTM STP 528)	Experimental: 3-hour EC50 >1000 mg/L (OECD 209)