Reaction products of 1H-Imidazole-1-ethanol, 4,5-dihydro-, 2-(C11-17 and C17 unsatd. alkyl) derivs. and sodium hydroxide and 2-propenoic acid

Endpoint summary

Description of key information

Lyophilised Amphopropionates C12 -18 (93.6% a.i.) has a greasy to resin-like consistency at 20 °C and 101.3 kPa (visual inspection during determination of melting/boiling point).

 

The melting temperature of lyophilised Amphopropionates C12 -18 (93.6% a.i.) was determined by differential scanning calorimetry and visual methods according to OECD Test Guideline 102 (adopted on 27 July 1995) and EU test method A.1 (1995). No thermodynamic melting point could be identified up to beginning degradation at 190 °C (1020 hPa). A sharp drop in viscosity from waxy solid to liquid (begin of fluidity) was observed in the range of 87 °C - 100 °C.

 

The boiling temperature of lyophilised Amphopropionates C12 -18 (96.3% a.i.) was determined by thermogravimetry and differential scanning calorimetry according to OECD Test Guideline 103 (adopted on 27 July 1995) and EU test method A.2. There was no boiling point detected. Test item decomposition was observed above 190 °C.

 

The density of Amphopropionates C12-18 (40% a.i. in water) was determined according to OECD guideline 109 and EU test method A.3 with the oscillating densitometer method. The density of Amphopropionates C12-18 in aqueous solution is 1.0349 g/cm³ at 20°C. The relative density is 1.035.

 

In accordance with column 2 of REACH Annex VII, a granulometry study does not need to be conducted as the test substance is manufactured and used in a non solid or granular form. Amphopropionates C12-18 is manufactured and used only in aqueous solution.

 

According to REACH Annex XI, 2. the determination of the vapour pressure of Amphopropionates C12-18 is not necessary, because it is technically not feasible: the expected value of vapour pressure for the pure substance cannot be measured due to residual content of solvent which results in a higher solvent vapour pressure than test substance vapour pressure. The residual content of solvent cannot be reduced below the limit of measurement with reasonable effort. As the substance is ionic/amphoteric, the vapour pressure of the pure substance is expected to be extremely low.

Supporting data are available from a calculation.

Amphopropionates C12-18 is a UVBC substance containing C8-, C10-, C12-, C14-, C16-, and C18-alkyl side chains. Based on this and the variable composition of the compound (alkyl chain distribution dependent on origin of the coco fatty acid) the calculation of physico-chemical properties for the mixture is not feasible. To get a hint on the physico-chemical data, the EPIWIN calculation was conducted for the C8 and the C18 derivatives. The vapour pressures were calculated using EPIWIN v3.20, MPBPWIN v1.42. The calculation yielded vapour pressures of 6E-23 mm Hg (8E-23 hPa) and 6.7E-27 mm Hg (8.9E-27 hPa; at 25°C each), respectively.

For chemical safety assessment, the lowest value accepted by IUCLID (1E-09 Pa) will be used.

 

The partition coefficient (n-octanol/water) of Amphopropionates C12-18 was determined according to EU method A.8 (1995) and OECD Guideline 117 (2004) by the HPLC method. The test was performed with a concentration of 3750 mg/L Amphopropionates C12-18 in 75 % methanol : 25 % buffer solution at pH 7 (phosphate, 50 mM).

The individual log Pow values for each of the test item components were 2.7 (C12), 3.98 (C14), 5.27 (C16), 5.52 (C18.1), 6.55 (C18) at a mean temperature of 23.7°C. A weighted average mean value of 3.43 was calculated based on the respective peak area percentages.

 

A test on water solubility is not required. The substance is manufactured and marketed as 40% aqueous solution. Thus, the substance is highly soluble in water (at least 400 g/L).

Supporting data are available which were obtained by calculating the water solubilities for the C8 and the C18 derivatives using EPIWIN v3.20, WSKOW v1.41. The calculation yielded water solubilities of 1000000 mg/L and 1396 mg/L (at 25°C) for the C8 and C18 derivatives, respectively, taking into account the log Kow values estimated via EPIWIN (C8: log Kow=-6.53; C18: log Kow=-1.62). Based on these results and the classification scheme the C8-derivative can be regarded as very soluble and the C18-derivative as soluble.

Using the fragment method, water solubilities of 787.26 mg/L (C8-derivative) and 0.004804 mg/L (C18-derivative) were estimated. According to the classification, the components can be regarded as moderately soluble (C8-derivative) and insoluble (C18-derivative).

 

The surface tension of Amphopropionate C12 -18 (water content 59.7%) was determined according to OECD Guideline 115 (27 July 1995) and EU Method A.5 by the OECD harmonized ring method. The mean surface tension of an aqueous test substance solution at 20°C at a concentration of 1 g/L, was determined to be 30.48 mN/m. Therefore Amphopropionate C12 -18 is considered to be surface active.

 

In accordance with REACh regulation, Annex VII, 7.9 a study on flash point is not required for aqueous solutions if it only contains volatile organic components with flash-points above 100°C.

The substance does only contain components with very low vapour pressures and it is manufactured and used only in water-based solutions. Supporting data obtained with a closely related substance suggest that the substance has no flash point below the boiling temperature of the test substance.

 

According to Annex XI, 1 testing of the auto flammability is scientifically not necessary. The substance is manufactured and used only as 40% (w/w) solution in water. Supporting data from a closely related substance further suggest that the aqueous solution of the substance has an auto-ignition temperature of >400°C.

 

According to Annex XI, 1 testing of flammability does is scientifically not necessary. Testing of flammability of solids is not necessary as the substance is only manufactured and used as 40% (w/w) solution in water. Testing of reactivity with water and testing of generation of flammable gases in contact with water is not necessary as a review of the structure suggests that there are no chemical groups present that would imply pyrophoric properties or flammability on contact with water. In addition experience in handling and use implies no pyrophoric properties or flammability on contact with water.

 

According to Reach Annex VII end point 7.11, a study on explosive properties does not need to be conducted if there are no chemical groups associated with explosive properties present in the molecule. The molecular structure of the test substance does not contain any chemically instable or highly energetic groups that might lead to an explosion.

 

The dissociation constants of Amphopropionate C12 (=main constituent of the UVCB substance) were calculated using the freely accessible online version of I-Lab 2.0 Algorithm Version: v5.0.0.184. The calculation yielded pKa of 3.6±0.4, 7.4±0.4, 14.3±0.5 and 15.4±0.5 at 25°C. The calculations show that there is no pH at which all ionisable groups are in their non-ionised form and that at pH 5.5 the net charge of Amphopropionate C12 is zero.

Additional information

Justification for read-across

For details on substance identity and detailed toxicological profiles, please refer also to the general justification for read-across given at the beginning of the CSR and attached as pdf document to IUCLID section 13.

This read-across approach is justified based on structural similarities. The target and source substances contain the same functional groups. Thus a common mode of action can be assumed.

 

Structural similarity and functional groups

The target substance Amphopropionates C12-18 is manufactured from fatty acids (C12-18, C18unsatd.) andaminoethylethanolamie (AEEA) to form 1H-Imidazole-1-ethanol, 4,5-dihydro-, 2-(C11-C17 odd-numbered, C17unsatd. alkyl) derivs. This is further reacted with 2-propenoic acid in the presence of sodium hydroxide (alternatively, sodium 2-propenoate can be used) and water. The molar relation between 1H-Imidazole-1-ethanol, 4,5-dihydro-, 2-(C11-C17, C17unsatd. alkyl) derivs. and 2-propenoic acid is somewhat below 1:1. Most of the excess 2-propenoic acid is stripped off by distillation. However, a small amount remains in the aqueous solution.

 

The source substance Amphoacetates C8-C18 is manufactured from 1H-Imidazole-1-ethanol, 4,5-dihydro-, 2-(C7-C17 odd-numbered, C17-unsatd. alkyl) derivs. and chloroacetic acid in the presence of sodium hydroxide. The molar relation between 1H-Imidazole-1-ethanol, 4,5-dihydro-, 2-(C7-C17 odd-numbered, C17-unsatd. alkyl) derivs. and chloroacetic acid ranges from 1:1 to 1:2. As by-product, hydrochloric acid is formed during the reaction, that is neutralized with adding more sodium hydroxide.

 

Differences

Propionate vs. acetate functions:

The target substance Amphopropionates C12-18 contains propionate functions, whereas the source substance Amphoacetates C8-C18 contains acetate functions. This difference is not considered to be relevant for flammability endpoints.

 

Presence of residual acrylic acid:

The target substance Amphopropionates C12-18 may contain some small amounts of residual acrylic acid, in contrast to the source substance Amphoacetates C8-C18. This difference is not considered to be relevant for flammability endpoints.

 

The provided structural similarities and impurity profiles support the proposed read-across hypothesis with high confidence.

 

	Target substance	Source substance
Endpoints	Amphopropionates C12-18	Amphoacetates C8-C18
Molecular weight	ca. 380 – ca. 440 g/mol	446 g/mol(major constituent)
Physical state at 20°C / 1013 hPa	Liquid (resin-like); manufactured, marketed and used in aqueous solutions	Solid (paste); manufactured, marketed and used in aqueous solutions
Melting point	no melting point identified ; sharp drop in viscosity from waxy solid to liquid (begin of fluidity): 87 °C - 100 °C   OECD TG 102 / EU method A.1; differential scanning calorimetry, visual methods    RL1; no GLP	no melting point identified   OECD TG 102 / EU method A.1; differential scanning calorimetry    RL1; GLP
Boiling point	no boiling point detected, decomposition >190°C   OECD TG 103 / EU method A.2; thermogravimetry and differential scanning calorimetry   RL1; no GLP	no boiling point detected, decomposition starting at 160 °C   OECD TG 103 / EU method A.2; differential scanning calorimetry   RL1; GLP
Surface tension	30.48 mN/m at 20°C and 1 g/L   OECD TG 115 / EU method A.5, ring method   RL1; GLP	34.0 mN/mat 20°C and 1 g/L   OECD TG 115 / EU method A.5, ring method   RL1; GLP
Water solubility	>/=400 g/L	> 1 kg/L at 20°C   OECD TG 105 / EU method A.6   RL1; GLP
Log Kow	3.43 at 23.7°C (weighted mean), range: 2.7 – 6.55   OECD TG 117 / EU method A.8   RL1; GLP	-1 at 20°C (0.64 to -4.19)   calculation; assumption based on n-octanol solubility + extremely high water solubility   RL1; GLP
Vapour pressure	8E-21 Pa at 25°C (C8 derivative)   Calculation; EPIWIN v3.20, MPBPWIN v1.42.   RL4, no GLP	1.47E-03 Pa at 20°C   OECD TG 104 / EU method A.4   RL1; GLP
Flash point	No data	No flash-point was observed below the boiling temperature (aqueous solution)   EU Method A.9 (Flash-Point; closed cup)   RL1; GLP
Auto flammability	No data	485°C at 1013.5 – 1016.5 hPa (aqueous solution)   EU method A.15   RL1; GLP

 

The physical state of the (neat) substances is resin-like to paste-like. Melting and boiling behaviour is comparable; no melting or boiling points could be detected; decomposition starts at 150 – 190°C. Both substances are highly soluble in water and show surface active properties. The vapour pressure of both substances is very low.

The partition coefficient of Amphoacetates C8-C18 was estimated by calculation, which may explain the rather different outcome compared to the target substance.

Both, target and source substance, are handled only as aqueous solutions. No flash-point was observed below the boiling temperature ofAmphoacetates C8-C18 (aqueous solution). The auto-ignition temperature ofAmphoacetates C8-C18 (aqueous solution) was >400°C.

 

Quality of the experimental data of the analogues:

The available data are adequate and sufficiently reliable to justify the read-across approach.

The test materials used in the respective studies represent the source substance as described in the hypothesis in terms of substance identity and minor constituents.

Overall, the study results are adequate for the purpose of classification and labelling and risk assessment.

 

Conclusion

The structural similarities between the source and the target substances presented above and in more detail in the general justification for read-across support the read-across hypothesis. Adequate and reliable scientific information indicates that the source and target substances have similar properties (non-flammable).

Thus, the results obtained with the source substance Amphoacetates C8-C18 in the available studies on flash-point and auto-flammability are considered to be also relevant for the target substanceAmphopropionates C12 -18.