N-[3-(trimethoxysilyl)propyl-1,3-Benzenedimethanamine

Vapour pressure

Link to relevant study record(s)

Reference

Endpoint:

vapour pressure

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016-01-27 to 2016-02-12

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 104 (Vapour Pressure Curve)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method A.4 (Vapour Pressure)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 830.7950 (Vapor Pressure)

Deviations:

no

GLP compliance:

yes

Type of method:

effusion method: by loss of weight or by trapping vaporisate

Key result

Test no.:

#1

Temp.:

20 °C

Vapour pressure:

0.004 Pa

Key result

Test no.:

#2

Temp.:

25 °C

Vapour pressure:

0.006 Pa

A representative weight loss curve of the test item is shown in Figure 4 (attached). The results of the isothermal TGA analysis with the test item and the vapour pressure at 20°C and 25°C are given in Table 1 and Table 2.

The vapour pressure regression curve constructed using the data of Experiment 1 and Experiment 2 had a coefficient of correlation of <0.99. Therefore, a third experiment was performed and the obtained data was included to calculate the coefficient of correlation for the three experiments. The coefficient of correlation was >0.99.

The plot of the log P_T of the test item as function of the reciprocal temperatures is shown in Figure 5 (attached).

The equation of the curve was: log PT = -4094 x 1/T + 11.52 (r = 0.990, n = 9).

 

Table 1 Results of the isothermal TGA analysis

Temperature [°C]	Weight loss [μg/min]	νT[g/cm^2/h]	log νT	log PT	PT [Pa]
120	8.607 7.658 7.886	1.03E-03 9.14E-04 9.41E-04	-2.99 -3.04 -3.03	1.14 1.08 1.10	14 12 13
130	13.97 12.28 13.23	1.67E-03 1.47E-03 1.58E-03	-2.78 -2.83 -2.80	1.38 1.32 1.35	24 21 23
140	24.04 20.63 22.16	2.87E-03 2.46E-03 2.65E-03	-2.54 -2.61 -2.58	1.65 1.57 1.61	45 38 41

 

Table 2: Vapour pressure of the test item

Temperature [°C]	log PT	PT [Pa]	PT [mmHg]
20	-2.45	3.6E-03	2.7E-05
25	-2.22	6.1E-03	4.6E-05

Conclusions:

Vapour pressure values of 3.6E-03 Pa at 20°C and 6.1E-03 Pa at 25°C were determined for the substance using a relevant test method and in compliance with GLP. The result is considered to be reliable.

Description of key information

Vapour pressure [whole substance]: 3.6E-03 Pa at 20°C and 6.1E-03 Pa at 25°C (OECD 104)

Vapour pressure [Constituent 1, N-[3-(trimethoxysilyl)propyl]-1,3-benzenedimethanamine]: 1.3E-03 Pa at 25°C (QSAR)

Vapour pressure [Constituent 2, 3-[(2,2-dimethoxy-1,2-azasilolidin-1-yl)benzenedimethanamine]: 9.7E-03 Pa at 25°C (QSAR)

Vapour pressure [N-[3-(trihydroxysilyl)propyl]-1,3-benzenedimethanamine]: <1.0E-03 Pa at 25°C (QSAR)

Vapour pressure [methanol]: 12790 Pa at 20°C

Key value for chemical safety assessment

Vapour pressure:

0.004 Pa

at the temperature of:

20 °C

Additional information

Vapour pressure values of 3.6E-03 Pa at 20°C and 6.1E-03 Pa at 25°C were determined for the whole substance using an isothermal thermogravimetric effusion method in accordance with OECD Test Guideline 104 and in compliance with GLP. The result is considered to be reliable.

The submission substance is a multi-constituent substance containing two main constituents. Measured vapour pressure for the whole substance is preferred for the purposes of human health exposure assessment while for the purposes of environmental hazard and fate assessment, the vapour pressures of the constituents are relevant. The vapour pressures of the individual constituents have been predicted using a validated QSAR estimation method. Vapour pressure values of 1.3E-03 Pa at 25°C and 9.7E-03 Pa at 25°C were obtained for N-[3-(trimethoxysilyl)propyl]-1,3-benzenedimethanamine (Constituent 1) and 3-[(2,2-dimethoxy-1,2-azasilolidin-1-yl)benzenedimethanamine (Constituent 2) respectively.

In contact with water, N-[3-(trimethoxysilyl)propyl]-1,3-benzenedimethanamine, hydrolyses rapidly to form N-[3-(trihydroxysilyl)propyl]-1,3-benzenedimethanamine and methanol.

3-[(2,2-Dimethoxy-1,2-azasilolidin-1-yl)benzenedimethanamine contains two types of chemical group that are susceptible to hydrolysis; the silyl amine (Si-N) group and the methoxy (Si-OMe) group. The Si-N bond is highly susceptible to hydrolysis by both acid-catalysed and base-catalysed mechanisms, and as such the silyl amine bond present in Constituent 2 will undergo very rapid hydrolysis on contact with water to form an intermediate hydrolysis product, N-[3 -(hydroxy(dimethoxy)silyl)propyl]-1,3 -benzenedimethanamine. The intermediate hydrolysis product, in turn undergoes rapid hydrolysis to form the same hydrolysis products as Constituent 1, N-[3-(trihydroxysilyl)propyl]-1,3-benzenedimethanamine and methanol.

The vapour pressure of the silanol hydrolysis product, N-[3-(trihydroxysilyl)propyl]-1,3-benzenedimethanamine has been estimated using the same validated QSAR estimation method as the main constituents. The predicted vapour pressure is <1.0E-03 Pa at 25°C.

Methanol has a reported vapour pressure of 12790 Pa at 25°C (OECD 2004)

 

Reference:

OECD (2004): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 18-20 October 2004, Methanol, CAS 67-56-1.