Asparagine

Endpoint summary

Additional information

L-asparagine is a white solid at 20°C and 1013 hPa (visual assessment).

The melting point of L-asparagine was reported in the CRC Handbook of Chemistry and Physics (84th Ed) and experimentally determined. In the DSC experiment two endothermic peaks could be observed (peak maxima: 109 °C/242 °C [first run] resp. 109 °C/ 240 °C [second run]). These two peaks correlated with maxima observed during the thermogravimetric measurement. Upon further heating the DSC-curve showed no more sharp peaks but the typical fluctuating course of decomposition.

The boiling point of L-asparagine hydrate was determined according to OECD guideline 103 using the Differential Scanning Calorimetry (DSC) method. Weight loss was recorded in three ranges; mass change in the range from 20- 180 °C: 11.9 %; mass change in the range from 180 to 280 °C: 24.2 %; mass change in the range from 280 to 600 °C: 32.9 %. The weight continuously decreased and reached a loss of approx. 69.1 % at 600 °C.

Since heating up to a tempearature of 240°C revealed no further endothermic peaks but the typical flunctuating course of degradation the substance is considered to decompose.

This assumption can also be deduced from the literature, as it is well known that amino acids tend to decompose (CRC Handbook of Chemistry and Physics (84th Ed).

No boiling point could be detected. The substance decomposes at a temperature > 250 °C.

The density of L-asparagine hydrate was determined according to OECD guideline 109 by means of a gas displacement pycnometer and information was gathered from a secondary source (CRC Handbook of Chemistry and Physics (84th Ed). A value of 1.54 g/cm³ at 20 °C was obtained from both sources.

The particle size of L-asparagine hydrate was determined according to OECD guideline 110 by means of the Laser diffraction method. The following mean particle sizes were measured: D10 = 78.2 µm, D50 = 251.2 µm, D90 = 514.0 µm.

The vapour pressure of L-asparagine was estimated using the EPISUITE QSAR program (EPISUITE v4.11) by the Modified Grain Method (MPBVP v1.43). A value of 0.000002266 Pa was obtained at 25 °C.

The vapour pressure was not experimentally measured due to residual content of solvent (water) 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.

The log Kow was gathered from reliable published data (Chmelik et al., 1991). A value of -3.82 was reported.

Sufficient infomation about the water solubility of L-asparagine was provided by handbook data (CRC Handbook of Chemistry and Physics (Ed. 84th)) which obtained a value of 25.1 g/L at 25 °C.

According to column 2 of the REACH regulation annex VII testing of surface tension of L-asparagine does not need to be conducted because based on the structure of L-asparagine the substance is considered to be not surface active.

The flammability of L-asparagine was experimentally determined using the method of Ciba-Geigy/Kühner. The combustion number of the substance was measured, i.e. for classification of L-asparagine the duration of burning was measured over a distance of 200 mm, if 200 mm of the test item are not burned within 45 s the substance is not classified as readily flammable.

According to REACH, Annex VII, column 2 the testing of flash point does not need to be conducted for solids, since the determination of flash point is only relevant to liquids and low melting point solids. The substance has a melting point of 235°C.

In accordance with column 2 of REACH regulation annex VII, explosive properties testing does not need to be conducted as there are no chemical groups associated with explosive properties in the molecule.

In accordance with column 2 of REACH regulation annex VII, oxidising properties testing does not need to be conducted as there are no chemical groups associated with oxidising properties in the molecule.