2-methylbutyl acrylate

Toxicity to aquatic algae and cyanobacteria

Description of key information

72-hour ErC50: 1.15 mg/L (OECD 201)
72-hour NOEC: 0.0403 mg/L (OECD 201)

Additional information

Toxicity of 2-methylbutyl acrylate (2-MBA) to algae was measured in a 72-hour OECD 201 assay with the green alga P. subcapitata  conducted under GLP criteria.  The results are considered reliable with restrictions.  The key result is similar to supporting test results for n-butyl acrylate (n-BA).  A 96-hour EbC50 of 2.65 mg/L to P. subcapitata was reported for n-BA (96 h NOEC: < 1.8 mg/L).  The n-BA study was considered reliable without restriction for n-BA, but as read-across to 2-MBA is reliable with restriction (Klimisch 2). 2-MBA and n-BA are acrylate esters which exert toxicity by virtue of electrophilic (Michael-type) addition to cellular nucleophiles such as glutathione⁽¹⁾or cellular proteins⁽²⁾.  The result of this addition is glutathione depletion followed by oxidative damage to cells, or alternatively protein inactivation.  Detoxification is by ester hydrolysis followed by downstream conversion and entry of acrylic acid to the citric acid cycle⁽³⁾.  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.  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.  In addition, n-BA has a slightly lower log Kow.  Taken together, n-BA may be slightly less toxic than 2-MBA with slightly faster detoxification (by ester hydrolysis), but is expected to have generally similar toxicity values.

 

References:

1. A. P. Freidig, H. J. M. Verhaar, J. L. M. Hermens.  1999.  Comparing the Potency of Chemicals with Multiple Modes of Action in Aquatic Toxicology:  Acute Toxicity Due to Narcosis versus Reactive Toxicity of Acrylic Compounds.  Env. Sci. Technol. 33 (17): 3038–3043.

2. K. Chan & P. J. O’Brien.  2008. Structure–activity relationships for hepatocyte toxicity and electrophilic reactivity of a,b-unsaturated esters, acrylates and methacrylates.  J. Appl. Toxicol. 28 (8): 1004–1015.

3.  H. Greim, J. Ahlers, R. Bias, B. Broecker, H. Hollander, H.-P. Gelbke, S. Jacobi, H.-J. Klimisch, I. Mangelsdorf, W. Mayr, N. Schön, G. Stropp, P. Stahnecker, R. Vogel, C. Weber, K. Ziegler-Skylakakis, E. Bayer.  1995.  Assessment of structurally related chemicals: Toxicity and ecotoxicity of acrylic acid and acrylic acid alkyl esters (acrylates), methacrylic acid and methacrylic acid alkyl esters (methacrylates).  Chemosphere 31 (2): 2637–2659.

 

 

Data matrix – Analog approach
	Target substance	Source substance
CHEMICALNAME	2-methylbutyl acrylate	n-butyl acrylate
CAS#	44914-03-6	141-32-2
Molecular formula	C8H14O2	C7H12O2
Molecular Weight	142.2	128.2
PHYSICO-CHEMICAL DATA
Melting Point	≤ -75 °C	Not available
Boiling Point	161.7 °C at 1013hPa	147 °C at 1013hPa
Density	0.8886 g/cm3 at 25 °C	0.9 g/cm3 at 20.0 °C
Vapour Pressure	1.7 hPa at 20°C	5 hPa at 22.2°C
Partition Coefficient (log Kow)	2.9	2.38 (at 25°C)
Water Solubility	316 mg/L at 23 °C	Not available
ENVIRONMENTAL FATE and PATHWAYS
Photodegradation	DT50 1.04 d (AOPWIN v1.92)	Not determined
Stability in Water	Adaptation, readily biodegradable	DT50, 1100 day at pH 7, 25 °C (40CFR796.3500)
Aerobic Biodegradation	60% after 11 days (OECD 301D)	80 - 90% after 28 days (OECD 310)
Bioconcentration	Not bioaccumulative (Low log Kow, extensive metabolism)	Not bioaccumulative (Low log Kow, extensive metabolism)
Transport and Distribution	Koc 263 – 302 (Calculated by TGD method)	Koc 40-148 (EPA OTS 796.2750)
Henry's Law constant	96 Pa*m3/mol at 23.1 °C	Not determined
ENVIRONMENTAL TOXICITY
Toxicity to Algae and Aquatic Plants (P. subcapitata)	72-hour ErC50: 1.15 mg/L (OECD 201)   72-hour NOEC: 0.0403 mg/L (OECD 201)	96-hour EbC50: 2.65 mg/L (OECD 201)   96-hour NOEC:< 1.8 mg/L (OECD 201)