N, N-bis-(2-hydroxyethyl) dimethyl ammonium methane sulfonate

Melting point / freezing point

Link to relevant study record(s)

Reference

Endpoint:

melting point/freezing point

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2021-02-02 to 2021-06-17

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method A.1 (Melting / Freezing Temperature)

Version / remarks:

European Commission Regulation (EC) No. 440/2008

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 102 (Melting point / Melting Range)

Version / remarks:

1995

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of method:

differential scanning calorimetry

Key result

Melting / freezing pt.:

>= 12 - <= 17 °C

Atm. press.:

1 013 hPa

Decomposition:

no

Remarks:

Not in the temperature range relevant for melting / freezing

Sublimation:

no

Within two DSC measurements the test item was cooled down to -80 °C with a cooling rate of 10 K/min, -80 °C were kept for 60 min and afterwards the test item was heated up to 500 °C with a heating rate of 10 K/min. During cooling down the measurements showed an exothermal effect (solidification) in the temperature range of (-10) – (-45 °C) and during heating up an endothermal effect (melting) in the temperature range of (-15) – 35 °C.
An additional DSC measurement was performed in which the test item was cooled down to -80 °C with a cooling rate of 10 K/min, -80 °C were kept for 60 min and afterwards the test item was heated up to 325 °C with a heating rate of 10 K/min. During cooling down the measurement showed an exothermal effect (solidification) in the temperature range of (-10) – (-50 °C) and during heating up an endothermal effect (melting) in the temperature range of (-5) – 40 °C.
The solidification most likely took place at lower temperatures than the melting due to supercooling. The onset temperature (melting, see Table 1) was derived from the intersection of the tangent line with the highest slope of the endothermal peak with the baseline.
The results of the DSC measurements are summarized in Table 1. Graphical presentations of the DSC runs are shown in Figure 1 and Figure 2 given in the illustration attached to this ESR.

Table 1: Melting point (DSC measurements)

Ident No.	Test item / mg	Starting temperature / °C	Final test temperature / °C	Temperature range (endothermal) / °C	Onset (melting) / °C	Crucible	Observations after the measurement
39439	12.18	‑80	500	10 – 35	16.16	Aluminium with a hole	Measurement continued after melting
39472	12.04	‑80	500	(-15) – 30	7.49	Aluminium with a hole	Measurement continued after melting
39494	39.05	‑80	325	(-5) – 45	16.97	Aluminium with a hole	Measurement continued after melting
39605	43.18	‑80	50	(-10) – 40	12.00	Aluminium with a hole	Brown-yellow viscous liquid
39609	28.22	‑80	50	(-5) – 35	12.15	Aluminium with a hole	Brown-yellow viscous liquid

 

The first three measured onset temperatures (Ident No. 39439, 39472 and 39494) differed from each other with 7.5 °C and 16.2°C and 17.0°C, respectively. It was assumed that the deviation might be due to the hygroscopic properties of the test item. Therefore, two additional measurements were carried out in which care was taken to ensure that the sample had as little contact with air as possible. In addition, the test item was cooled down more slowly during the repeated measurements to give the molecules more time to arrange into an ordered state. Therefore, within the two repeated DSC measurements the test item was cooled down to -80 °C with a cooling rate of 1 K/min, -80 °C were kept for 300 min and afterwards the test item was heated up to 50 °C with a heating rate of 10 K/min. During cooling down the measurements showed an exothermal effect (solidification) in the temperature range of (-5) – (-10 °C) and during heating up an endothermal effect (melting) in the temperature range of (-10) – 40 °C. The repeated measurements showed a sharper endothermal effect on cooling (solidification), but the endothermal effect associated with melting was still broad and the onset temperatures varied from the ones measured before.
Graphical presentations of the additional DSC runs are shown in Figure 3 given in the illustration attached to this ESR.
In summary, the test item melted within a wide range in the performed DSC measurements and the onset temperatures varied. For the final result of the melting the DSC measurement Ident No. 39472 was not taken into account as a shoulder was observed, that was not observed in the other four measurements.
According to the literature, the formation of a stable crystal lattice is hindered in ionic liquids by charge delocalisation and steric effects. The latter is probably the reason for the broad endothermal peaks of the melting. Therefore, a melting range of approx. 12 °C to 17 °C was given as final result for the test item.

 

Conclusions:

Melting range (OECD TG 102; A.1; DSC): 12-17 °C

Executive summary:

The melting point (range) of the test item was measured by DSC measurements. Four repeated determinations were used as a basis for the melting range. Due to a wide range observed based on a cooling / heating rate of 10 K/min and 60 min at -80 °C, further two independent measurements were performed with a reduced heating / cooling rate of 1 K/min and 300 min at -80 °C. In addition, contact with air was reduced to the minimum experimentally possible to exclude any effect of humidity on the hygroscopic test item. Still, results were comparable, and it was concluded that the broad melting range might be a consequence of the nature of the substance: according to the literature, the formation of a stable crystal lattice is hindered in ionic liquids by charge delocalisation and steric effects.
The melting range was determined as the range of observed onset temperatures derived from four valid experiments.
Accordingly, test item MAT-144 had a melting range according to European Commission Regulation (EC) No. 440/2008, A.1. as well as OECD 102 (1995) of 12 °C to 17 °C.

Description of key information

Melting range (OECD TG 102; A.1; DSC): 12-17 °C; the key value given below represents the arithmetic mean of the minimum (12°C) and maximum (17°C) of the range measured.

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:

14.5 °C

Additional information

The melting point (range) of the test item was determined by DSC measurements. Four repeated determinations were used as a basis for the melting range. Due to a wide range observed based on a cooling / heating rate of 10 K/min and 60 min at -80 °C, further two independent measurements were performed with a reduced heating / cooling rate of 1 K/min and 300 min at -80 °C. In addition, contact with air was reduced to the minimum experimentally possible to exclude any effect of humidity on the hygroscopic test item. Still, results were comparable, and it was concluded that the broad melting range might be a consequence of the nature of the substance: according to the literature, the formation of a stable crystal lattice is hindered in ionic liquids by charge delocalisation and steric effects.
The melting range was determined as the range of observed onset temperatures derived from four valid experiments.
Accordingly, test item MAT-144 had a melting range according to European Commission Regulation (EC) No. 440/2008, A.1. as well as OECD 102 (1995) of 12 °C to 17 °C.