N-(N6-trifluoroacetyl-L-lysyl)-L-proline

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:

1993-05-25 to 1993-07-27

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:

1984

Deviations:

no

GLP compliance:

yes

Type of method:

differential scanning calorimetry

Remarks:

and photocell detection method

Key result

Atm. press.:

1 013 Pa

Decomposition:

yes

Decomp. temp.:

>= 370 K

Sublimation:

no

Remarks on result:

other: No melting until decomposition

RESULT OF THE PRELIMINARY TESTS:

The test substance ε-trifluoroacetyl-L-lysyl-L-proline showed no real melting point or melting range. The detection of the melting range with the Mettler thermosystem was caused only by the changing of optical properties of the test substance.

RESULTS OF THE DSC-ANALYSIS:

In the temperature range of 370 K up to 405 K a slight exothermal proceeding was detected. No endothermal reaction which could show a melting or boiling was seen.

RESULTS FROM THE METTLER THERMOSYSTEM:

The results of the three determinations were:

a) 362.7 K b) 362.9 K C) 359.2 K

But as described in the preliminary test this values only show the temperature at the point the light-transmission reached 20%.

RESULTS FROM THE BUCEI MELTING POINT APPARATUS:

Every change in optical properties of the test substance took place in a large temperature range. Therefore no exact melting point resulted.

In the following table the temperature ranges are shown in which the particular events took place.

356.1 K - 365.7 K: The optical properties of the test substance were varying. They were changing slowly from white, over milky to transparent. But no totally clear liquid was reached. In every case there were a few small bubbles inside the substance. Also in this temperature range a volumetric contraction was recognizable. But at the end of this range the substance wasn't a real liquid. It is better described as gel-like.

365.7 K - 370 K: In the lower area of the capillary tube a gaseous bubble was built. Above the bubble was the test substance. The substance became milky again.

370 K - 390 K: Anew the substance became transparent.

390 K - 406 K: The substance rose inside the capillary tube.

Conclusions:

Summarizing the results stated above and the DSC analysis it can be reported, that the test substance ε-Trifluoroacetyl-L-lysyl-L-proline neither got an exact melting point nor a fixable melting range. The behavior of the test substance is better described as softening.
The DSC-analysis showed no endothermal proceedings, which must take place in the case of melting or boiling. But beginning at about 370 K a small exothermal proceeding was detected. This could signal a decomposition of the test substance.

Description of key information

The substance decomposes at a temperature above 97 °C (> 307 K) before the melting point is reached.