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EC number: 500-148-0
CAS number: 61788-89-4
The Dimerised fatty acids and its derivatives category covers C16 - C18
unsaturated fatty acids derived monomers, dimers and trimers, as well as
their hydrogenated products in different proportions and in accordance
with their corresponding production and purification processes. They are
all prepared by the dimerisation of C16 - C18 unsaturated fatty acids.
As UVCB substances derived from natural sources, members of this
category are chemically similar as they are all essentially a complex
mixture of C16 - C18 unsaturated and saturated, branched and linear
fatty acids, their monomers, dimers and trimers with varying structural
geometric isomers. All substances in the category have an overlap in
regard to their composition. With reference to information of existing
categories, the category of Dimerised Fatty Acids and Its Derivatives is
based on similar physicochemical and toxicological properties and 2
sub-categories are further defined on the basis of their environmental
fate and toxicity. The first sub-category covers three monomeric
(by-)products of the dimerization process (readily biodegradable
substances). The second sub-category covers the predominately oligomers
(dimeric and trimeric products) of dimerization based on their lack of
ready biodegradability and other environmental fate properties.
Sub-category 1: predominantly monomers
Fatty acids, C16-18 and C18-unsaturated, branched and linear
Hydrogenated monomer acid
Octadecanoic acid, branched and linear
Sub category 2: predominantly oligomers (dimers, trimers)
Fatty acids, C16-C18 and C18-unsaturated, dimerized
Fatty acids, C18-unsaturated, dimers
Fatty acids, C18-unsaturated, dimers, hydrogenated
Fatty acids, C18-unsaturated, trimers
Derived from the same starting substance, all substances in this
category have a homologous composition of fatty acids with a C16 - C18
carbon chain in diverse forms, that is susceptible to oxidation through
metabolic processes. In view of the results of various QSAR analyses,
the toxic hazard of these substances mainly depends on the number of
carbons, on the chain “structure”, such as branching, unsaturation,
grade of cyclics and aggregation, as well as on their position in the
whole molecular structure. In contrast, the number of the functional
group “carboxylic acids” has no significant influence on the tox- and
Sub category 2: predominantly Oligomers (dimers, trimers)
Environmental Fate Sub-category 2:
Due to the chemical structure of Fatty acids, C18-unsaturated,
dimers (CAS No. 61788-89-4) and the very low water solubility (< 0.12
mg/L, limit of detection) hydrolysis does not contribute to abiotic
degradation in the aquatic environment. Photodegradation of Fatty acids,
C18-unsaturated, dimers (CAS No. 61788-89-4) in air is not a relevant
degradation pathway as the vapour pressure under ambient conditions is
negligible. The biodegradation screening test with Fatty acids,
C18-unsaturated, dimers (CAS No. 61788-89-4) revealed the potential for
persistence in the environment with biodegradation rates below 10 %
within 28 days (ready biodegradability test).
The adsorption potential is predicted by QSAR modeling (EPISUITE KOCWIN
v2.00). The main factor determining the log Koc value of fatty acids is
the carbon chain length. For "predominantly monomers", the log Koc is in
the range 4 < log Koc < 5. For "predominantly oligomers", the log Koc is
> 5. In both cases, a high adsorption to organic carbon in soils and
sediments is expected.
The test substance has estimated log Kow values outside the range
0 to 6. Additionally, chromatograms contain peaks at retention times
corresponding to partition coefficients outside this range. In mobile
phase adjusted to pH 2, only hydrophilic components (tR< 2 min; ca. 20 %
of total area) have been eluted and detected under the chromatographic
conditions employed. Based on the preliminary solubility of the test
item in octanol and water and taking into consideration all the
limitations of the test design, the log Kow of Fatty Acids, C-18
unsaturated, dimers (CAS No. 61788-89-4) should be judged to be > 4. For
this reason, adsorption to organic carbon in soils and sediments is
If a substance has a low potential for bioaccumulation and/or a
low potential to cross biological membranes then studies on
bioaccumulation are not required. This is the case for the dimerised
fatty acids, and in particular for Fatty acids, C18-unsaturated, dimers
(CAS No. 61788-89-4).
Due to the potential of these substances to adsorb (log Koc > 5, log Kow
>4) one may assume that the uptake may occur through the ingestion of
soil or sediment. However, uptake of dimers and trimers is expected to
be low based on the fact that the Dimerised Fatty Acids are relatively
large molecules (C36 as dimers and C54 as trimers) with high molecular
weights (dimeric acids 561 g/mol, trimeric acids 838 g/mol). Thus,
according to Lipinski’s rule of five, they have a low potential to cross
biological membranes (Lipinski et al., 2001).
As fatty acids are naturally
stored in the form of triacylglycerols primarily within fat tissue until
they are used for energy production (fat storage tactic), it is
concluded that there will be no risk to organisms from
bioconcentration/biomagnification of fatty acids.
Finally, as the Dimerised Fatty Acids have a low water solubility
(sub-category 2 dimers and trimers: all < 0.52 mg/L) the concentration
in water is expected to be low and consequently also the exposure to the
aquatic environment, if occurring at all.
Hence, Fatty acids, C18-unsaturated, dimers (CAS No. 61788-89-4) does
not pose a risk to organisms in regard to
Hsieh, A. and Perkins, E.G. (1976). Nutrition and Metabolic Studies of
Methyl Ester of Dimer Fatty Acids in the Rat. Lipids, 11(10):763-768.
Lipinski et al. (2001) Experimental and computational approaches to
estimate solubility and permeability in drug discovery and development
settings, Adv. Drug Del. Rev., 2001, 46, 3-26.
Paschke, R.F. et al. (1964). Dimer acid structures. The dehydro-dimer
from methyl oleate and Di-t-butyl peroxide. Journal of the American Oil
Chemists' Society 41(1):56-60.
U.S.Environmental Protection Agency (2009). Risk-Based Prioritization
Document. Initial Risk-Based Prioritization of High Production Volume
(HPV) Chemicals – Fatty Acid Dimers and Trimer Category. pp 1-19. Report
date: April 2009.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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