Trichloro(hexadecyl)silane

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

13 Mar 2015

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

The study was conducted according to an appropriate OECD test guideline but was not in compliance with GLP.

Qualifier:

according to guideline

Guideline:

EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)

Version / remarks:

(in analogy to OECD test guideline
111)

Deviations:

no

GLP compliance:

no

Remarks:

Iso 9001:2008 certified 2015-03-11 TÜV Süd Management Service GmbH

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

Samples could not be prepared because the test item (CAS 005894-60-0) hydrolyzes immediately in water with formation of insoluble products. Thus, a determination of the solubility of the test item in water and its hydrolysis kinetics is not possible.

Buffers:

- pH: 4.0; 7.0 and 9.0
- Composition of buffer:
pH 4: CertiPur, Citric acid + hydrochloric acid + sodium hydroxide, company Merck
pH 7: Baker Analyzed, Potassium dihydrogen phosphate + disodiumhydrogen phosphate, company J. T. Baker
pH 9: CertiPur, Boronic acid + potassium chloride + sodium hydroxide, company Merck

Transformation products:

not measured

pH:

4

DT50:

<= 2 min

pH:

7

DT50:

< 2 min

pH:

9

DT50:

< 2 min

Details on results:

A determination of the solubility of SILAN HEXADECYL in water and its hydrolysis kinetics was not possible since suitable samples for kinetic 1H NMR spectroscopic measurements could not be prepared because of very fast hydrolysis and precipitation of solids. The halflife times were thus assumed to be much smaller than 2 min.

Table 1: Results

Parameter	Result	Method
Degradation – Abiotic	t1/2 (pH 4) = <<2 min	EC test guideline C.7 (in analogy to OECD testing method 111)
Degradation - Hydrolysis as a Function of pH	t1/2 (pH 7) = <<2 min
	t1/2 (pH 9) = <<2 min

Description of key information

Hydrolysis half-life: << 2 minutes

Additional information

One hydrolysis study according to EC test guideline C.7 (in analogy to OECD test guideline 111) is available for the test substance. A determination of the solubility of Trichloro(hexadecyl)silane in water and its hydrolysis kinetics was not possible since suitable samples for kinetic 1H NMR spectroscopic measurements could not be prepared because of very fast hydrolysis and precipitation of solids. The half-life times were thus assumed to be much smaller than 2 min. This is also the case for other chlorosilanes for which measured data is available. These substances are in the same analogue group of chemicals which hydrolyse rapidly (PFA, 2013).

For several chlorosilanes, quantitative half-life data at 1.5ºC are available; further studies found no parent substance to be present at t0, indicating extremely rapid hydrolysis in any of these cases. The measured half-lives at pH 4, 7 and 9 are all within seconds at 1.5°C.

The hydrolysis products for the registered substances are hexadecylsilanetriol and hydrochloric acid (PFA, 2016).

Table: Hydrolysis half-lives at pH 4, 7 and 9 for chlorosilanes.

CAS	Name	Result – half-life at pH4 (seconds)	Result – half-life at pH7 (seconds)	Result – half-life at pH9 (seconds)	Temperature	Klimisch
75-77-4	Chlorotrimethylsilane	7	11	8	1.5 ± 0.5˚C	2a
75-78-5	Dichloro(dimethyl)silane	10	17	7	1.5 ± 0.5˚C	2a
75-79-6	Trichloro(methyl)silane	7	9	6	1.5 ± 0.5˚C	2a
80-10-4	Dichloro(diphenyl)silane	6	10	8	1.5 ± 0.5˚C	2a
675-62-7	Dichloromethyl(3,3,3-trifluoropropyl)silane	8	12	9	1.5 ± 0.5˚C	2a
4518-98-3	1,1,2,2-tetrachloro-1,2-dimethyldisilane	8	7	7	1.5 ± 0.5˚C	2a
5578-42-7	Dichlorocyclohexylmethylsilane	<<27 min^1	<27 min^1	<27 min^1	27°C	2a
13154-25-1	Chlorotri(3-methyl-propyl)silane	<<2.4 h ^1	<<2.4 h ^1	<<2.4 h ^1	50°C	1a
5894-60-0	Trichloro(hexadecyl)silane	<<2 min^1	<<2 min^1	<<2 min^1	Room temperature	2a

¹No parent substance was identified at t0; therefore, no half-life could be determined.