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Physical & Chemical properties

Melting point / freezing point

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Reference
Endpoint:
melting point/freezing point
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH
see "General Justification for Read-Across" attached to IUCLID section 13

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Mutual read across from the AAPBs to one another is justified:

a) Based on the information given in section 1, it can be concluded that all AAPBs mentioned above are similar in structure, since they are manufactured from similar resp. identical precursors under similar conditions and all contain the same functional groups. Thus a common mode of action can be assumed.
b) The content of minor constituents in all products are comparable and differ to an irrelevant amount.
c) The only deviation within this group of substances is a minor variety in their fatty acid moiety, which is not expected to have a relevant impact on intrinsic toxic or ecotoxic activity and environmental fate. Potential minor impact on specific endpoints will be discussed in the specific endpoint sections.

The read-across hypothesis is based on structural similarity of target and source substances. Based on the available experimental data, including key physico-chemical properties and data from toxicokinetic, acute toxicity, irritation, sensitisation, genotoxicity and repeated dose toxicity studies, the read-across strategy is supported by a quite similar toxicological profile of all five substances.
The respective data are summarised in the data matrix; robust study summaries are included in the Technical Dossier in the respective sections.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
see "General Justification for Read-Across" attached to IUCLID section 13

3. ANALOGUE APPROACH JUSTIFICATION
see "General Justification for Read-Across" attached to IUCLID section 13

4. DATA MATRIX
see "General Justification for Read-Across" attached to IUCLID section 13
Reason / purpose:
read-across: supporting information
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Key result
Atm. press.:
1 013 hPa
Decomposition:
yes
Decomp. temp.:
60 - 260 °C
Remarks on result:
not determinable
Remarks:
melting point not identifyable due to decomposition

Description of key information

C8 -18 and C18 unsatd. AAPB: fraction C8/C18: m.p.: 208°C; fraction C8/C10: m.p.: 55-60°C; fraction C12/C14: m.p.: 69-187°C
C8-18 AAPB: not identifyable due to decomposition of the test substance in the range between 208 and 280°C
C12 AAPB: not identifyable due to decomposition of the test substance in the range between 60 and 260°C

Key value for chemical safety assessment

Additional information

In studies conducted according to OECD Guideline 102, the melting points of C8 -18 AAPB and C12 AAPB were investigated using differential scanning calorimetry (DSC). Melting points were not identifyable due to decomposition at temperature ranging from 208 to 280 (C8 -18 AAPB) and 60 and 260°C (C12 AAPB). Based on these results it can be assumed that a weak chemical bond is present in the molecule which is unstable towards elevated temperatures. All AAPBs are similar in structure, contain all the same zwitterionic structure. They differ, however, by their carbon chain length distribution and the degree of unsaturation (<=20%) in the fatty acid moiety. The content of minor constituents in all products are comparable and differ to an irrelevant amount. Based on the available data, it can be assumed that chain length distribution and degree of unsaturation of the fatty acid chain have no or at the most a minor impact on this endpoint.

 

The melting points of the different fractions of C8 -18 and C18 unsatd. AAPB determined via the capillary method are judged as not reliable as the method does not distinguish between a real melting process and a reaction/decomposition process and as comparable temperatures were found as decompostion temperature in the DSC measurements.