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EC number: 252-558-1
CAS number: 35435-21-3
is a liquid at standard temperature and pressure, with a measured
melting point of <-20°C at 1013 hPa and a measured boiling point of
237.2°C at 1013 hPa. It has a measured relative density of 0.876 at
20°C, a measured kinematic viscosity of 1.98 mm2/s at
20°C and measured vapour pressure values of 0.14 Pa and 0.22 Pa at 20°C
and 25°C respectively.
The substance is classified as
Category 3 flammable liquid in accordance with Regulation (EC) No.
1272/2008 on the basis of a measured flash point of 42°C at 1013 hPa and
a measured boiling point of 237.2°C at 1013 hPa. It has a measured
auto-ignition temperature of 251°C at 964 -967 hPa, and is not explosive
and not oxidising on the basis of chemical structure.
In contact with water, the
substance hydrolyses at a moderate rate (half-lives of 0.9 h at pH 4, 43
h at pH 7 and 0.5 h at pH 9 and 20-25°C) resulting in the formation of
(2,4,4-trimethylpentyl)silanetriol and ethanol according to the
(CH3)3CCH2CH(CH3)CH2Si(OCH3CH2)3+ 3H2O → (CH3)3CCH2CH(CH3)CH2Si(OH)3 + 3CH3CH2OH
The substance has an estimated log
Kow value of >6.5 and a measured water solubility of <0.1
mg/L at 20°C.
Due to the moderate hydrolysis of
the substance in contact with water, the key physicochemical properties
of the hydrolysis products are presented below.
is miscible with water, has low log Kow (-0.3) and high
vapour pressure (7910 Pa at 25°C).
saturation concentration in water of the silanol hydrolysis product,
is limited by condensation reactions to approximately 200 mg/L. However,
it is very hydrophilic (calculated solubility is 2.4E+05 mg/L using a
QSAR method). (2,4,4-Trimethylpentyl)silanetriol is
not surface active and is much less volatile than the parent substance
with a predicted vapour pressure of 1.2E-04 Pa at 25°C and a predicted
log Kow of 0.9.
The first dissociation constant of a structurally analogous
silanetriol (phenylsilanetriol) has been reported to be around pKa =
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