Ethoxytrimethylsilane

Henry's Law constant

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

Henry's law constant

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please refer to analogue justification provided in IUCLID section 13

Reason / purpose for cross-reference:

read-across source

H:

-2.77 dimensionless

Temp.:

25 °C

Remarks on result:

other: log Kaw

H:

4.2 Pa m³/mol

Temp.:

25 °C

H:

2 Pa m³/mol

Temp.:

12 °C

Average log Kaw was found to be -2.77 ± 0.10 for TMS at 25.0 °C.

This is equivalent to a dimensional Henry's law constant value of 4.2 Pa m³ mol-1.

Conclusions:

A log Kaw value of -2.77± 0.10 at 25.0°C was determined for trimethylsilanol. This is equivalent to a dimensional Henry’s Law Constant of 2.0 Pa m³/mol at 12°C (4.2 Pa m³/mol at 25°C).

Reference 2

Endpoint:

Henry's law constant

Type of information:

experimental study

Adequacy of study:

key study

Study period:

26/05/2011

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

The study was well documented and meets generally accepted scientific principles, but was not conducted in compliance with GLP.

Principles of method if other than guideline:

This study used a custom-made glass apparatus which allowed the establishment of an octanol/air/water equilibrium for simultaneous determination of Kaw, Koa and Kow. The apparatus consisted of two air-tight syringes with an air sampling port in one syringe and a water sampling port on the other. The air phase in both syringes was connected through a valve during the equilibrium, but the valve was closed during sampling. Samples were collected from the air and water phases from 1 to 90 hours to establish attainment of equilibrium in the system. Air samples were collected using a cryogenic gas trap. Water samples were extracted using a two-step procedure.

H:

-2.77 dimensionless

Temp.:

25 °C

H:

4.2 Pa m³/mol

Temp.:

25 °C

H:

2 Pa m³/mol

Temp.:

12 °C

Average log Kaw was found to be -2.77 ± 0.10 for TMS at 25.0°C.

This is equivalent to a dimensional Henry's law constant value of 4.2 Pa m3 mol-1.

Conclusions:

A log Kaw value of -2.77± 0.10 at 25.0°C was determined for trimethylsilanol. This is equivalent to a dimensional Henry’s Law Constant of 2.0 Pa m³/mol at 12°C (4.2 Pa m³/mol at 25°C).

Description of key information

Henry’s Law Constant: 2.0 Pa m³/mol at 12°C (4.2 Pa m³/mol at 25°C).

Key value for chemical safety assessment

Henry's law constant (H) (in Pa m³/mol):

2

at the temperature of:

12 °C

Additional information

Ethoxytrimethylsilane (CAS 1825-62-3) hydrolyses rapidly in water to trimethylsilanol and ethanol (half-life = 2.2 min at 25 °C and pH 7). Due to the very fast hydrolysis of the parent substance the assessment of volatility is only relevant for the hydrolysis products. In accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5 “Grouping of substances and read-across” and in accordance with the read across assessment framework (RAAF, ECHA 2017) a read-across from the hydrolysis product trimethylsilanol (CAS 1066-40-6) has been applied to support the environmental hazard assessment of ethoxytrimethylsilane. Details on the read across justification can be found in the overall justification for grouping of substances attached in IUCLID Section 13.

This study used a custom-made glass apparatus which allowed the establishment of an octanol/air/water equilibrium for simultaneous determination of Kaw, Koa and Kow. The apparatus consisted of two air-tight syringes with an air sampling port in one syringe and a water sampling port on the other. The air phase in both syringes was connected through a valve during the equilibrium, but the valve was closed during sampling. Samples were collected from the air and water phases from 1 to 90 h to establish attainment of equilibrium in the system. Air samples were collected using a cryogenic gas trap. Water samples were extracted using a two-step procedure. A log Kaw value of -2.77± 0.10 at 25.0°C was determined for trimethylsilanol. This is equivalent to a dimensional Henry’s Law Constant of 2.0 Pa m³/mol at 12°C (4.2 Pa m³/mol at 25°C). This value will be used for the environmental risk assessment.