5′-O-(4,4′-dimethoxytrityl)-2′-deoxythymidine-3′-O-[O-(2-cyanoethyl)-N,N′-diisopropylphosphoramidite]

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:

2017-09-18 to 2018-02-01

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 102 (Melting point / Melting Range)

Deviations:

no

GLP compliance:

no

Type of method:

hot stages

Key result

Atm. press.:

ca. 1 atm

Decomposition:

yes

Decomp. temp.:

ca. 145 °C

Remarks on result:

other: No melting point could be determined. Substance only showed a softening effect in the temperature range between 55 - 75 °C, followed by decomposition at a temperature of approx. 145 °C.

Two DSC measurements with a heating rate of 10 K/min showed an endothermal effect in the temperature range of 55 °C – 75 °C.

The first DSC measurement with a final temperature of 500 °C additionally showed an exothermal effect starting at approx. 145 °C, indicating the decomposition of the test item. The decomposition of the substance was confirmed by the appearance of the sample after measurement (black residue) combined with a mass loss of 74 % of the initial weigh-in (see table).

The second measurement was terminated at 120 °C to ensure that the endothermal effect is the melting/softening effect.

The results of the DSC measurements are summarized in the table below:

DSC run	Weigh-in / mg	Starting temperature	Final test temperature	Temperature range (endo-thermal) / °C	Onset / °C	Crucible	Observations after the measurement
1	12.14	25	500	55 – 75	59.32	Aluminium with a hole	Black residue Mass loss: 74%
2	12.64	25	120	55 – 75	60.38	Aluminium with a hole	Test item was a white solidified melt Mass loss: -

The test item showed an unusually low energy consumption during the endothermal effect (<10 J/g). Therefore it was concluded that the test item did not actually melt. The test item most likely softened in the temperature range of 55 °C – 75 °C. No additional endothermal effects were observed after the softening and before the exothermal effect at approximately 145 °C indicated a decomposition of the test item.

Conclusions:

The observed low endothermal effect indicated only a softening (energy consumption < 10 J/g) of the test item. The test item softened in the temperature range between 55 – 75 °C under atmospheric conditions and started to decompose at a temperature of approx. 145 °C.

Executive summary:

The melting point / melting range of the test item was determined by DSC measurement according to OECD 102. The study showed that the test item has no exact melting point but shows an unusual softening in the temperature range between 55 - 75 °C. The result "softening and no actual melting" was concluded because of the unusually low energy consumption during the endothermal effect (<10 J/g). No additional endothermal effects were observed after the softening and before the exothermal effect at approximately 145 °C that indicated a decomposition of the test item.

Description of key information

The melting point / melting range of the test item was determined by DSC measurement according to OECD 102. The study showed that the test item has no exact melting point, but shows an unusual softening in the temperature range between 55 - 75 °C.

Additional information

The result "softening and no actual melting" was concluded because of theunusually low energy consumption during the endothermal effect (<10 J/g).No additional endothermal effects were observed after the softening and before the exothermal effect at approximately 145 °C that indicated a decomposition of the test item.