5'-O-(p,p'-dimethoxytrityl)thymidine

Vapour pressure

Link to relevant study record(s)

Reference

Endpoint:

vapour pressure

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017-11-03 to 2018-02-14

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 104 (Vapour Pressure Curve)

Qualifier:

according to guideline

Guideline:

EU Method A.4 (Vapour Pressure)

GLP compliance:

no

Type of method:

effusion method: vapour pressure balance

Temp.:

20 °C

Vapour pressure:

< 0 Pa

Temp.:

25 °C

Vapour pressure:

< 0 Pa

Temp.:

50 °C

Vapour pressure:

< 0 Pa

The vapour pressure was measured in the temperature range of 30 °C to 120 °C. The measured vapour pressures at the corresponding temperatures are listed in Table 1 below. The mass of test item was determined (with Sartorius R200D) before and after the vapor pressure measurement. A mass loss of approx. 1.3% (w/w) was observed. The weight loss correpsonds to the content of volatile constituents (water and acetonitrile) in the test item.

Table 1: Measured vapour pressures and corresponding temperatures

Temperature / °C	Vapour pressure / hPa
30.1	1.5 x 10E-5
40.3	2.1 x 10E-5
50.3	1.9 x 10E-5
60.3	1.4 x 10E-5
70.3	7.9 x 10E-6
80.3	6.3 x 10E-6
90.3	7.5 x 10E-6
100.3	4.1 x 10E-6
110.3	3.0 x 10E-6
120.2	2.9 x 10E-6

The data points measured at 30 °C to 50 °C could not be used for a regression of the vapour pressure curve because only the first two values show the expected increase of vapour presssure with increasing temperature. Regarding the decreasing vapour pressure beginning at 50 °C, these results show a typical deviation caused by volatile impurities at the beginning of a measurement. Since the measured mass loss is in the magnitude of the known acetonitrile and water content, the measured vapour pressures above 1 x 10E-5 hPa can be assigned to the effect of these light boiling impurities. The results for the temperatures above 60 °C were below the detection limit (1 x 10E-5 hPa). Since the test did not yield vapour pressures sufficiently high to extrapolate to 20, 25, and 50 ^oC, these values were estimated using the Antoine equation. The detection limit (1 x 10E-5 hPa) at the highest measurement point (120 °C) was used for the calculation as the measured vapour pressures were below the detection limit.

Conclusions:

The vapour pressure of the test item 5’-O-(4,4’-Dimethoxytrityl)thymidine was determined according to the OECD guidline 104 by effusion method using a vapour pressure balance. The vapour pressure was measured in the temperature range of 30 °C to 120 °C. However, the measured values were below the detection limit and therefore the vapour pressures for 20 °C, 25 °C and 50 °C were estimated using the Antoine equation:
20 °C: < 4.6 x 10E-8 Pa;
25 °C: < 8.9 x 10E-8 Pa;
50 °C: < 1.8 x 10E-6 Pa.

Executive summary:

The vapour pressure of the test item 5’-O-(4,4’-Dimethoxytrityl)thymidine was determined according to the OECD guidline 104 by effusion method using a vapour pressure balance. The vapour pressure was measured in the temperature range of 30 °C to 120 °C. However, the measured values were below the detection limit and therefore the vapour pressures for 20 °C, 25 °C and 50 °C were estimated using the Antoine equation:

20 °C: < 4.6 x 10E-8 Pa;

25 °C: < 8.9 x 10E-8 Pa;

50 °C: < 1.8 x 10E-6 Pa.

This is a conservative estimation of the vapour pressure of the test item for the listed temperatures.

Description of key information

The vapour pressure of the test item 5’-O-(4,4’-Dimethoxytrityl)thymidine was determined according to the OECD guidline 104 by effusion method using a vapour pressure balance. The vapour pressure was measured in the temperature range of 30 °C to 120 °C. However, the measured values were below the detection limit and therefore the vapour pressures for 20 °C, 25 °C and 50 °C were estimated using the Antoine equation:

20 °C: < 4.6 x 10E-8 Pa;

25 °C: < 8.9 x 10E-8 Pa;

50 °C: < 1.8 x 10E-6 Pa.

This is a conservative estimation of the vapour pressure of the test item for the listed temperatures.

Key value for chemical safety assessment

Vapour pressure:

0 Pa

at the temperature of:

20 °C