Synthesis of alkoxybenzylmethylsilanes and polybenzylmethylsiloxane polymers on their basis

Article abstract of DOI:10.1007/s11172-015-1183-0

An efficient solvent-free procedure for the preparation of alkoxybenzylmethylsilanes by organomagnesium synthesis was developed. The reaction conditions gave the high yields of the target products. A number of benzylmethylsiloxane polymers was synthesized by polycondensation of alkoxybenzylmethylsilanes in anhydrous acetic acid. The products obtained can become a good alternative to phenylsiloxanes in some practical applications.

Full text of DOI:10.1007/s11172-015-1183-0

Russian Chemical Bulletin, International Edition, Vol. 64, No. 10, pp. 2498—2504, October, 2015
2498
Synthesis of alkoxybenzylmethylsilanes
and polybenzylmethylsiloxane polymers on their basis
S. A. Milenin,a A. A. Kalinina,a V. V. Gorodov,a N. G. Vasilenko,a M. I. Buzin,b and A. M. Muzafarova,b
aN. S. Enikolopov Institute of Synthetic Polymeric Materials, Russian Academy of Sciences,
70 ul. Profsoyuznaya, 117393 Moscow, Russian Federation.
Fax: +7 (495) 335 9000
bA. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 5085. Eꢀmail: aziz@ispm.ru
An efficient solventꢀfree procedure for the preparation of alkoxybenzylmethylsilanes by
organomagnesium synthesis was developed. The reaction conditions gave the high yields of the
target products. A number of benzylmethylsiloxane polymers was synthesized by polycondensaꢀ
tion of alkoxybenzylmethylsilanes in anhydrous acetic acid. The products obtained can become
a good alternative to phenylsiloxanes in some practical applications.
Key words: organoalkoxysilanes, organomagnesium synthesis, alkoxybenzylmethylsilanes,
polycondensation, polybenzylmethylsiloxanes.
The introduction of aromatic fragments into the comꢀ
ride at the temperature considerably below 100 °C. The
benzyl group also can be removed upon treatment with
sodium metal.3,4 Therefore, in the cases when a latent
functionality at the silicon atom is required, for example,
a stable protecting group, the use of the benzyl group has
clear advantages. However, since the first S. Kipping's
works there are practically no publications dealing with
the synthesis and studies of properties of the benzylꢀconꢀ
taining siloxane products, except of several works in which,
however, no efficient procedures for the preparation of
such polymers were suggested.5—8 At the same time, the
new approaches to the synthesis of alkoxy functional benꢀ
zylmethylsilanes and polybenzylmethylsiloxanes on their
basis open a possibility of various applications for these
compounds.
position of polyorganosiloxanes increases their oxidation,
thermal, and thermooxidation stability.1 The most studꢀ
ied phenylꢀsubstituted polyorganosiloxanes are already
widely used in practice. It was found that phenyl groups in
polymethylphenylsiloxane also stabilize the methylsiloxꢀ
ane fragments. The presence of phenyl substituents leads
to the improvement of physical and mechanical properties
of siloxane polymers. Polybenzylmethylsiloxanes are anꢀ
other type of organosilicon polymers containing an aroꢀ
matic group. They are studied poorly and yet have no pracꢀ
tical application, while the benzylsiloxane products of oliꢀ
gomeric and cyclic structure were obtained by S. Kipping
using a hydrolytic polycondensation of dibenzylchlorosiꢀ
lane and benzyldichloroethylsilane just at the beginning of
20th century.2 The chemical stability of the benzyl group
at the silicon atom as compared to the phenyl substituent
was also studied at that time. An increased stability of
benzyl siloxane polymers to strong acids as compared to
the phenyl analogues is the most attractive property from
the practical point of view. Thus, the phenyl group can be
substituted by the hydroxy one with the cleavage of benꢀ
zene upon treatment with concentrated sulfuric acid at
the temperature below 100 °C, whereas the benzyl group
under the same conditions remains at the silicon atom.
Conversely, in the alkaline medium the Si—Ph bond is
stable under very drastic conditions, while the Si—CH2—Ph
fragment disintegrates relatively easy with the liberation of
toluene. Both substituents (phenyl and benzyl) eliminate
from the silicon atom upon treatment with aluminum chloꢀ
Results and Discussion
Synthesis of alkoxybenzylsilanes. One of the reason for
the lack of studies of benzylꢀcontaining siloxanes is the
shortage of efficient methods for the preparation of the
starting compounds, functional benzylsilanes. Since the
polycondensation of organoalkoxysilanes was shown to be
the most acceptable method for the preparation of polyorꢀ
ganosiloxanes from both technological and environmenꢀ
tal points of view, we developed the synthesis of alkoxy
functional benzylsilanes. Organometallic synthesis which
uses the Grignard reaction is the most convenient method
for the preparation of arylꢀcontaining functional silanes.
This method was used in the preparation of benzylchloꢀ
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2498—2504, October, 2015.
1066ꢀ5285/15/6410ꢀ2498 © 2015 Springer Science+Business Media, Inc.

Synthesis of polybenzylmethylsiloxanes
Russ.Chem.Bull., Int.Ed., Vol. 64, No. 10, October, 2015
2499
rosilanes in the laboratory practice.2,9—11 Alkoxybenzylsiꢀ
lanes were generally obtained by esterification of chlorosiꢀ
lanes, except the works,12,13 in which a possibility of orgaꢀ
nometallic synthesis of such monomers was demonstrated
based on triꢀ and tetraalkoxysilane, but the yield of the
target products was below 10%. We carried out a search
for the optimal conditions for the organomagnesium synꢀ
thesis of benzylethoxymethylsilanes in high yield of the
target products and the minimal technological risks. Inꢀ
dustrially available MeSi(OEt)3 and Me2Si(OEt)2 were
used as the starting compounds (Scheme 1).
Silane BnMe2SiOEt was obtained according to a simiꢀ
lar procedure with a twoꢀfold excess of diethoxydimethylꢀ
silane and magnesium relative to benzyl chloride. The
highest yield of the target product was 65%.
To sum up, the optimization of the reaction condiꢀ
tions allowed us to obtain the target compounds in high
yield, whereas the absence of diethyl ether in the reaction
medium considerably increased the processability of the
method.
Specific feature of organomagnesium synthesis of benꢀ
zylethoxymethylsilanes is that there is no need to activate
the reaction by standard activators such as dibromoetꢀ
hane, iodine, or phenyl bromide used in similar reactions
for the preparation of ethoxymethylphenylsilanes. This is
explained by the high enough activity of benzyl chloride as
compared to phenyl chloride in the Grignard reaction.
The process is activated spontaneously with an extensive
evolution of heat upon addition of reagents.
Scheme 1
Another advantage of the suggested synthesis of benꢀ
zylꢀsubstituted silanes is a possibility of preparation of
BnMeSi(OMe)2, whereas the synthesis of phenylꢀsubꢀ
stituted methoxysilanes is not feasible. The yield of
BnMeSi(OMe)2 at the ratio of the starting reagents
BnCl : MeSi(OMe)3 : Mg equal to 1.0 : 2.5 : 1.5 was 67%.
In conclusion, the studies of the synthesis of
BnMeSi(OEt)2, BnMeSi(OMe)2, and BnMe2SiOEt in
nonetherial medium showed that the preparation of these
compounds has a number of advantages as compared to
the processes of preparation of their phenyl analogues.
The reaction with benzyl chloride does not require activaꢀ
tion of the reaction mixture, the reaction begins spontaneꢀ
ously upon reflux, is accompanied by evolution of heat,
which maintains the reflux of the reaction mixtures. In the
process of preparation of benzylethoxysilanes, a small
amount of a side product bibenzyl was obtained, which
was formed by the mechanism of Wurtz reaction. It is not
toxic, in contrast to biphenyl formed in the similar process
of preparation of ethoxyphenylsilanes. The yield of alkoꢀ
xybenzylsilanes was ~70%, that is higher than the yield of
the methylphenyl analogues.
Synthesis of polybenzylmethylsiloxanes. Nowadays, the
most promising method for the preparation of polyorgaꢀ
nosiloxanes based on organoalkoxysilanes is the polyconꢀ
densation in the "active medium", anhydrous acetic acid,
which plays the role of both the reagent and the solvent.
It was shown earlier that this process is a complex of the
cascade interrelated reactions proceeding with participaꢀ
tion of water formed in the course of esterification reacꢀ
tion between acetic acid and alcohol. The alcohol, in turn,
is formed in the acetoxylation of alkoxysilane.15 The
formed water in situ is consumed in the hydrolysis reacꢀ
tion of acetoxysilyl groups. Then, the heterofunctional
condensation of silanols with acetoxysilyl groups results in
the formation of the siloxane bond. The acetic acid formed
at this stage returns back to the reaction cycle. This mechꢀ
The process was carried out in the absence of organic
solvents in the excess of alkoxysilane.14 To optimize the
synthesis, we varied the ratio of reagents involved in the
process and found the ratio providing the highest yield of
the target product (Table 1).
The data obtained showed that the excesses of magꢀ
nesium and triethoxymethylsilane have a noticeable inꢀ
fluence on the result of the reaction. The maximal yield of
the target product (70%) was reached at the molar ratio
MeSi(OEt)3 : BnCl : Mg = 2.5 : 1.0 : 1.5 (see Table 1,
entry 3). A further increase in the content of these reagents
relative to the amount of BnCl practically did not lead to
the change in the yield of the target product.
Table 1. The yield of BnMeSi(OEt)2 depending on the
ratio of reagents
Entry
Ratio of reagents/mol
Yield
(%)
MeSi(OEt)3
BnCl
Mg
1
2
3
4
5
1.6
2.0
2.5
3.0
3.0
1.0
1.0
1.0
1.0
1.0
0.8
1.5
1.5
1.1
2.0
16.1
46.5
70.0
37.2
71.0

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Russ.Chem.Bull., Int.Ed., Vol. 64, No. 10, October, 2015
Milenin et al.
anism explains a number of specificities and advantages of
this procedure: the process in all the stages proceeds in the
homogeneous medium, is well controlled, and makes it
possible to prepare polymeric product with a required
structure.
The polycondensation of BnMeSi(OEt)2 in the excess
of anhydrous acetic acid led to the formation of a mixture
of linear oligomers with terminal hydroxy groups and cyꢀ
clic compounds (Scheme 2), which is typical of the proꢀ
cesses of polycondensation of difunctional organosilicon
monomers.
ples at the 100% conversion of the Si—OEt groups. The
reaction product was also analyzed by GPC and IR specꢀ
troscopy.
To determine the amount of terminal hydroxy groups,
we carried out the blocking of obtained oligobenzylmethꢀ
ylsiloxanes with chlorotrimethylsilane (Scheme 3) under
conditions allowing to retain the composition of the startꢀ
ing products (GPC data), but with a full conversion of the
hydroxy groups, which was confirmed by the absence in
the IR spectra of the blocked samples of the absorption
band in the region of 3100—3600 cm–1 characteristic of
the SiOH groups.
When the polycondensation was carried out simply by
mixing the reagents, the reaction product was a ~50%
mixture of linear and cyclic oligomers with ~20 mol.%
content of terminal hydroxy groups. We studied a possibilꢀ
ity of increasing the process selectivity. As it was menꢀ
tioned above, in the polycondensation of organoalkoxysiꢀ
lanes in anhydrous acetic acid the water necessary for the
hydrolysis is generated in the esterification reaction, the
rate determining step of the process. It was shown earlier
that the composition of the reaction products can be conꢀ
trolled varying the rate of water generation in the condenꢀ
sation process. Slowing the rate of the liberation of water
in the system leads to a predominant formation of linear
oligomers, whereas an increase in the rate favors formaꢀ
tion of cyclic oligomers.16
Cyclic benzylmethylsiloxanes can be of interest as
monomers for preparation of polybenzylmethylsiloxanes
by polymerization. For their selective formation in the
process of polycondensation of BnMeSi(OEt)2 in aceꢀ
tic acid, it is necessary to increase the rate of liberation
of water, which, as it was shown earlier, can be reached
by the addition of an alcohol into the reaction mixture.
The addition of ethanol during polycondensation of
BnMeSi(OEt)2 in the active medium allowed us to inꢀ
crease the content of cyclic components to 75% with
the fairly high content of valuable cyclotrisiloxane (Taꢀ
ble 2).
Scheme 2
The reaction was monitored by the changes in the inꢀ
tensity of signals of the protons of the ethoxysilyl groups in
the 1H NMR spectrum of the reaction mixture samꢀ
a
7.27
7.0 6.0
5.0 4.0 3.0
2.0 1.0
0
δ
δ
b
To increase the content of linear oligomers in the prodꢀ
uct, the synthesis was carried out by a gradual addition of
BnMeSi(OEt)2 to the refluxing acetic acid in order to
decrease the rate of the formation of ethanol and, thereꢀ
fore, water in the reaction mixture (Table 3) as compared
to the experiment with the simultaneous mixing of reꢀ
agents. However, the expected effect of the increase in the
selectivity of the process (the growth of the amount of
7.27
7.0 6.0 5.0
4.0 3.0 2.0 1.0
0
Fig. 1. 1H NMR spectra of the starting benzylmethyldiethoxysiꢀ
lane (a) and the condensation product (b).
Scheme 3

Synthesis of polybenzylmethylsiloxanes
Russ.Chem.Bull., Int.Ed., Vol. 64, No. 10, October, 2015
2501
Table 2. The influence of the reaction conditions of polycondensation of BnMeSi(OEt)2 in acetic acid with
additives of ethanol on the yield of cyclosiloxanes
Entry
Ratio of reagents
/mol
Yield of
cyclosiloxanes
(%)
Content in the product*
(%)
BnMeSi(OEt)2
AcOH
EtOH
[BnMeSiO]3
[BnMeSiO]4
1
2
3
4
1
1
1
1
3
3
10
10
0.5
5
0.5
5
51
76
38
74
39
58
28
50
12
18
10
24
*GPC data.
Table 3. The condensation of benzylmethyldiethoxysilane in
1
acetic acid
2
3
Reaction
Yield (%)
conditions
4
Linear
Cyclic
oligomer
oligomer
5
Simultaneous mixing
of reagents
Slow addition
of alkoxysilane
50
66
50
34
linear products by ~10%) was considerably smaller than in
the case of methylphenyl oligomers (~40%).16
5
10
t/min
Fig. 2. The GPC curve of the starting oligomer (1), the products
of homocondensation of the starting oligomer at 50 (2), 10 (3),
160 °C (4), and the product of catalytic condensation of the
starting oligomer in the presence of potassium acetate (5).
The linear oligomers with terminal hydroxy groups are
promising starting compounds for both the development
of different polymeric compositions and the preparation
of highꢀmolecularꢀweight polymers. It is known that the
molecular weight of linear polycondensation oligomeric
products can be increased by the homocondensation of
terminal hydroxysilyl groups. The process of highꢀtemꢀ
perature condensation in the temperature range 50—160 °C
(in vacuo and in the absence of catalysts) did not lead to
a noticeable effect: the GPC data showed that the content
of both the cyclic components and the linear oligomers
remained the same (Fig. 2, curves 1—4). The use of
a catalytic amount of potassium acetate resulted in the
considerable increase in the molecular weight of the polyꢀ
mer (see Fig. 2, curve 5). The polybenzylmethylsiloxane
was obtained with the molecular mass of 7000 a.m.u. The
process was not accompanied by the unwanted depolyꢀ
merization, the content of cyclic products in the mixture
did not increase.
To sum up, the polycondensation of dialkoxybenzylmꢀ
ethylsilane in the active medium makes it possible to obꢀ
tain cyclic and linear benzylmethylsiloxanes. The alternaꢀ
tion of the reaction conditions allows one to change the
ratio of cyclic and linear oligomers in the reaction prodꢀ
uct. The catalytic homocondensation of hydroxy funcꢀ
tional linear oligomers leads to the formation of highꢀ
molecularꢀweight benzylmethylsiloxanes.
The new organosilicon arylꢀcontaining polymer, viz.,
the linear polybenzylmethylsiloxane, has the physicoꢀ
chemical properties practically similar to those of its
known analogue polymethylphenylsiloxane. The introducꢀ
tion of the methylene spacer between the phenyl group
and the silicon atom did not noticeably change the thermal
properties of the polymer. The glass transition temperatures
of polymethylphenylsiloxane and polybenzylmethylsiloxꢀ
ane of close molecular masses (MM ~ 30000 a.m.u.) are
practically the same: –22 °C for polymethylphenylsiloxꢀ
ane17 and ~–(20—22) °C for polybenzylmethylsiloxane
(DSC data) (Fig. 3).
The new arylꢀcontaining polymer is characterized by
the high thermal stability: the thermal decomposition of
the polymer starts at 370 °C (Fig. 4). The mass loss upon
heating of polymethylphenylsiloxane begins at the same
temperatures.17 The processes of thermooxidation destrucꢀ
tion in both cases begin in the region of 250 °C. The TGA
curves of the benzylmethyl polymers (both in air and in an
inert gas) has a shoulder at ~400 °C attributed, apparentꢀ
ly, to the crossꢀlinking process of the polymeric chains
through the hydrocarbon bridges upon the loss of phenyl

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Russ.Chem.Bull., Int.Ed., Vol. 64, No. 10, October, 2015
Milenin et al.
ing unlike units in the final product.18 This procedure was
used to synthesize a benzylꢀcontaining organosilicon coꢀ
polymer. To compare the properties, the ratio of methyl
and benzyl substituents and the amount of branching meꢀ
thylsilsesquioxane units were chosen the same as in the
industrial methylphenyl product (Scheme 4).
exo
–90
–60
–30
0
30
t/°С
Fig. 3. The DSC thermogramm of polybenzylmethylsiloxane.
To decrease the amount of lowꢀmolecularꢀweight cyꢀ
clic products, the reaction was carried out by a slow addiꢀ
tion of a solution of monomers in acetic acid to the refluxꢀ
ing acetic acid. The GPC data indicate that the polyconꢀ
densation product is characterized by a bimodal distribuꢀ
tion of molecular masses, with the content of the oligoꢀ
meric part being 80% (Mpica 1100 a.m.u.). The IR spectra
of the obtained oligomer exhibits the bands attributed to
the residual hydroxy groups, the amount of which assessed
substituents. However, the general picture of thermal staꢀ
bility is not affected by this process. It can be concluded
that he thermal stability of polybenzylmethylsiloxane is
not inferior to that of known methylphenylsiloxane anaꢀ
logues.
It is known that even a small amount of phenyl substitꢀ
uents in the composition of methylsiloxane copolymers
determines a number of valuable characteristics and, first
of all, extends the temperature range of the efficient exꢀ
ploitation of the material, for example, as organosilicon
liquids. The efficiency of the effect of aromatic substituꢀ
ents depends not only on their amount, but also on their
distribution in macromolecule. It was shown earlier that
the polycondensation of organoalkoxysilanes in anhydrous
acetic acid is the optimal method for the preparation of
copolymeric products, which provide the absence of hoꢀ
mofunctional impurities, the uniformity of the copolymer
chain structure, and a full agreement between the amount
of comonomers taken for the reaction and the correspondꢀ
1
from the H NMR spectrum of the sample blocked with
chlorotrimethylsilane is 1.6% (Fig. 5).
The presence of hydroxy groups was used for the
increase of the copolymer molecular mass. In the abꢀ
sence of catalysts, the process was not successful. Thereꢀ
fore, we carried out a catalyzed postꢀcondensation of
the hydroxy groups. It was interesting to conduct this
reaction in the presence of acidic catalysts, which canꢀ
not be used in the case of copolymers with phenyl subꢀ
stituents because of the instability of phenylsiloxane
bond in acidic media. The use of sulfuric acid as the
catalyst allowed us to increase the molecular mass of
the product to 3500 a.m.u.
m (wt.%)
100
1
2
1
50
2
200
400
600
t/°С
5
10
τ/min
Fig. 4. The TGA curves of polybenzylmethylsiloxane in air (1)
and in an inert gas (2).
Fig. 5. The GPC curves of copolycondensation product after
reaction (1) and after evacuation (2).
Scheme 4

Synthesis of polybenzylmethylsiloxanes
Russ.Chem.Bull., Int.Ed., Vol. 64, No. 10, October, 2015
2503
m (wt.%)
and a JETSTREAM 2 PLUS thermostat (KNAUER, Gerꢀ
many). T.p. 40 °C (+/–0.1 °C). Eluent THF, the flow rate
1.0 mL min–1, 300×7.8 mm columns, sorbent Phenogel (Pheꢀ
nomenex, USA), 5 μm, pore size from 103 to 105 Å. IR spectra
were recorded on a Bruker Equinox 55/S spectrometer.
100
80
60
40
20
0
DSC analysis of the samples was carried out on a MetTꢀ
BLerꢀ822e differential scanning calorimeter, the rate of heating
10 deg min–1. TGA analysis of the samples was carried out on
a DerivatografꢀK instrument (MOM, Hungary), the rate of heatꢀ
ing 5 deg min–1
.
1
Benzylmethyldiethoxysilane. A mixture of MeSi(OEt)3 (445 g,
2.5 mol) and BnCl (126.5 g, 1 mol) was added to Mg (36 g, 1.5 mol)
with reflux and stirred for 6 h at 150 °C. After addition of toluene
(600 mL), the mixture was filtered, toluene and MeSi(OEt)3
were evaporated. The product was isolated by distillation in vacꢀ
uo. B.p. = 120—122 °C (14 mBar). The yield was 70%. 1H NMR
(CDCl3), δ: 0.05 (s, 3 H, SiCH3); 2.19 (s, 2 H, SiCH2C6H5);
7.21—7.09 (m, 5 H, SiCH2C6H5); 3.78—3.70 (m, 4 H,
Si(OCH2CH3), J = 6.71 Hz), 1.19 (t, 6 H, Si(OCH2CH3), J =
= 6.71 Hz).
2
200
400
600
t/°С
Fig. 6. The TGA curves of benzylmethylsiloxane copolymer in
air (1) and in an inert gas (2).
Benzylmethyldimethoxysilane was obtained and isolated acꢀ
cording to a similar procedure based on MeSi(OMe)3. B.p. =
= 95—96 °C (14 mBar). The yield was 67%. 1H NMR (CDCl3),
δ: 0.08 (s, 3 H, SiCH3); 2.22 (s, 2 H, SiCH2C6H5); 7.27—7.08
(m, 5 H, SiCH2C6H5); 3.51 (s, 9 H, Si(OCH3)3).
exo
–120
–90
–60
—30
t/°С
Benzyldimethylethoxysilane was obtained and isolated accordꢀ
ing to a similar procedure based on Me2Si(OEt)2. The yield was
65%. H NMR (CDCl3), δ: 0.08 (s, 6 H, SiCH3); 2.18 (s, 2 H,
SiCH2C6H5); 7.21—7.04 (m, 5 H, SiCH2C6H5); 3.69—3.60
(m, 2 H, Si(OCH2CH3), J = 7.33 Hz); 1.17 (t, 3 H, Si(OCH2CH3),
J = 6.71 Hz).
Fig. 7. The DSC thermogramms of benzylmethylsiloxane coꢀ
polymer.
1
The TGA (Fig. 6) and DSC results (Fig. 7) indicate
a good thermal stability of the synthesized benzylmethylꢀ
siloxane copolymer. Its thermal properties are similar to
those of the phenylꢀcontaining copolymer.18
In conclusion, the introduction of the benzyl substituꢀ
ent in the composition of siloxane polymers of both the
homoꢀ and the copolymeric structure leads to the formaꢀ
tion of compounds whose thermal characteristics are not
inferior to those of methylphenylsiloxane compounds and
possessing an increased stability to acidic media. A practiꢀ
cal possibility for the preparation of such compounds is
determined by feasible synthesis of dialkoxybenzylmethꢀ
ylsilane developed by us.
Polycondensation of BnMeSi(OEt)2 in anhydrous AcOH.
A mixture of BnMeSi(OEt)2 (19.1 g, 0.086 mol) and AcOH
(51.6 g, 0.86 mol) was refluxed until the signals for the protons of
the ethoxy group completely disappeared from the 1H NMR
spectra of the reaction mixture samples. Then, toluene was addꢀ
ed to the reaction mixture, which was washed with water until
neutrality. The resulting solution was dried with sodium sulfate
and filtered, the solvent was evaporated. Oligobenzylmethylsiꢀ
loxane was obtained in quantitative yield. 1H NMR (CDCl3), δ:
0.16—0.39 (m, 3 H, (CH3)(C6H5CH2)Si); 2.16—2.40 (m, 2 H,
(CH3)(C6H5CH2)Si); 7.25—7.66 (m, 5 H, (CH3)(C6H5CH2)Si).
IR (CCl4), ν/cm–1: 3100—3600 (SiOH). The amount of the OH
groups 1.8% (the data from the 1H NMR spectra of the samples
blocked with chlorotrimethylsilane). GPC: MMpica = 900 a.m.u.
(58%), 500 a.m.u. (42%).
Experimental
The condensation of BnMeSi(OEt)2 in anhydrous AcOH
with a slow addition of BnMeSi(OEt)2 was carried out according
to a similar procedure, using a dosing unit for the addition of
BnMeSi(OEt)2. 1H NMR (CDCl3), δ: 0.16—0.40 (m, 3 H,
(CH3)(C6H5CH2)Si); 2.16—2.39 (m, 2 H, (CH3)(C6H5CH2)Si);
Starting reagents. Methylalkoxysilanes, chlorotrimethylsiꢀ
lane, toluene, THF, hexane, ethanol were purified according to
the general procedures.19 Acetic acid was dried by distillation
over P2O5.
7.24—7.68 (m, 5 H, (CH3)(C6H5CH2)Si). IR (CCl4), ν/cm–1
:
1H NMR spectra were recorded on a BrukerWPꢀ250 SY specꢀ
trometer in CDCl3, using the ACD LABS program. GLC analyꢀ
sis was carried out on a Khromatek Analitik 5000 instrument
(Russia) with katharometer as a detector, carrier gas helium,
2 m×3 mm columns, stationary phase SEꢀ30 (5%) deposited on
ChromatonꢀHꢀAW, the Khromatek Analitik program (Russia).
GPC analysis was carried out on a chromatographic system comꢀ
prising a STAIER high pressure pump (Akvilon, Russia),
a SmarTBLine RI 2300 refractometer (KNAUER, Germany),
3100—3600 (SiOH). The amount of the OH groups 1.9%
(the data from the 1H NMR spectra of the samples blocked
with chlorotrimethylsilane). GPC: MMpica = 900 a.m.u. (66%),
500 a.m.u. (34%).
The condensation of BnMeSi(OEt)2 in anhydrous AcOH
with EtOH was carried out according to a similar procedure with
the addition of anhydrous ethanol to the reaction mixture. Oliꢀ
gobenzylmethylsiloxane was obtained in quantitative yield.
1H NMR (CDCl3), δ: 0.15—0.38 (m, 3 H, (CH3)(C6H5CH2)Si);

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Russ.Chem.Bull., Int.Ed., Vol. 64, No. 10, October, 2015
Milenin et al.
2.17—2.50 (m, 2 H, (CH3)(C6H5CH2)Si); 7.26—7.65 (m, 5 H,
(CH3)(C6H5CH2)Si).
with water to рH 7, and dried with sodium sulfate. After filtraꢀ
tion, the volatile products were removed in vacuo at 300 °C. The
yield was 75%. 1H NMR (CDCl3), δ: 7.04—7.18 (m, 5 H,
(C6H5CH2)(CH3)2Si); 1.97—2.09 (m, 2 H, (C6H5CH2)(CH)2Si),);
(m, 6 H, (CH3)2Si); –0.04—0.01 (m, 9 H, (CH3)3Si). GPC:
MMpica = 3600 a.m.u., nd20 = 1.4825.
Blocking of terminal hydroxy groups of oligobenzylmethylsiꢀ
loxanes. A 20% solution of oligobenzylmethylsiloxane (0.54 g,
0.004 mol) in anhydrous toluene was added dropwise to a mixꢀ
ture of chlorotrimethylsilane (0.82 g, 0.007 mol) and pyridine
(0.59 g, 0.007 mol) in toluene (10 mL). The mixture was refluxed
with stirring for 4 h. The product was washed with water until
neutrality, dried with sodium sulfate, and evacuated at 50 °C. 1H
NMR (CDCl3), δ: 0.15—0.39 (m, 9 H, (CH3)3Si); 0.15—0.39
References
1. C. M. Murphy, C. E. Saunders, D. C. Smith, Ind. Eng. Chem.,
1950, 42, 2462.
(m,
3 H, (CH3)(C6H5CH2)Si); 2.16—2.40 (m, 2 H,
(CH3)(C6H5CH2)Si); 7.25—7.66 (m, 5 H, (CH3)(C6H5CH2)Si).
IR (CCl4), ν/cm–1: the signals of the SiOH groups in the region
of 3300 cm–1 are absent.
2. R. Robison, F. S. Kipping, J. Chem. Soc., Trans., 1908, 93, 439.
3. F. S. Kipping, Proc. R. Soc. London, 1937, 159, 139.
4. A. R. Steele, F. S. Kipping, J. Chem. Soc., 1928, 1431.
5. H. Y. He, H. X. Liao, W. X. Zhang, L. M. Wu, C. X. Zhao,
Res. Chem. Intermediates, 1997, 23, 41.
6. D. Häbich, F. Effenberger, Synthesis, 1979, 11, 841.
7. F. J. Feher, T. A. Budzichowski, J. Organomet. Chem., 1989,
373, 153.
8. E. O. Dare, L. K. Liub, J. Peng, Dalton Trans., 2006, 3668.
9. C. Eaborn, A. R. Hancock, W. A. Stacczyk, J. Organomet.
Chem., 1981, 218, 147.
10. D. Wrobel, R. Tacke, U. Wannagat, U. Harder, Chem. Ber.,
1982, 115, 1694.
Synthesis of linear highꢀmolecularꢀweight polybenzylmethylꢀ
siloxane. A mixture of oligobenzylmethylsiloxane (1 g, 0.007 mol)
and AcOK (1 wt.%) in acetic acid was stirred for 5 h in vacuo
(1 Torr) at 180 °C. The product was dissolved in toluene, washed
with DI water, and dried with sodium sulfate. The solvent was
evaporated in vacuo (1 Torr) at 50 °C. The yield of the product
was 0.88 g (88%). IR (CCl4), ν/cm–1: the signals in the region of
3100—3600 cm–1 (SiOH) are absent. GPC: MMpica = 6000 a.m.u.
(72%), 500 a.m.u. (28%). 1H NMR (CDCl3), δ: 0.16—0.40 (m, 3 H,
(CH3)(C6H5CH2)Si); 2.16—2.39 (m, 2 H, (CH3)(C6H5CH2)Si);
7.24—7.68 (m, 5 H, (CH3)(C6H5CH2)Si).
11. S. Kohama, Nippon Kagaku Zassi, 1960, 81, 11.
12. A. L. Reilly, H.W. Post, J. Am. Chem. Soc., 1951, 73, 865.
13. M. G. Voronkov, A. Y. Yakubovskaya, J. Gen. Chem. USSR,
1955, 25, 1124 [Zh. Obshch. Khim., 1955, 1124].
Copolycondensation of diethoxydimethylsilane, benzylmethꢀ
yldiethoxysilane, trimethylmethoxysilane, and triethoxymethylsiꢀ
lane in acetic acid. A mixture of diethoxydimethylsilane (144.3 g,
0.97 mol), benzylmethyldiethoxysilane (150.6 g, 0.67 mol), triꢀ
ethoxymethylsilane (12 g, 0.067 mol), trimethylmethoxysilane
(14 g, 0.134 mol), and anhydrous acetic acid (543.6 g, 7.25 mol)
was slowly added dropwise to anhydrous acetic acid (543.6 g,
7.25 mol) with stirring and reflux. IR (CCl4), ν/cm–1: the signals
in the region of 3100—3600 cm–1 (SiOH) are present. The
amount of the OH groups 1.6% (the data from the 1H NMR
spectrum of the blocked sample). The volatile products were
14. K. A. Andrianov, O. I. Gribanova, Russ. J. General Chem.
(Engl. Transl.), 1938, 552 [Zh. Obshch. Khim., 1938, 552].
15. E. V. Egorova, N. G. Vasilenko, N. V. Demchenko, E. A.
Tatarinova, A. M. Muzafarov, Dokl. Chem. (Engl. Transl.,
2009, 424, 15 [Dokl. Akad. Nauk, 2009, 424, 200].
16. A. A. Bychkova, F. V. Soskov, A. I. Demchenko, P. A. Storꢀ
ozhenko, A. M. Muzafarov, Russ. Chem. Bull. (Int. Ed.),
2011, 60, 2384 [Izv. Akad. Nauk, Ser. Khim., 2011, 2337].
17. Polymer Data Handbook, Ed. J. E. Mark, Oxford University Press,
New York, 2009, 840.
18. P. G. Alekseev, I. I. Skorokhodov, P. I. Povarnin, Svoistva
kremniiorganicheskikh zhidkostei [Properties of Organosilicon
Liquids], Energoatomizdat, Moscow, 1997, 19 (in Russian).
19. W. L. F. Armarego, D. D. Perrin, Purification of Laboratory
Chemicals, Butterworth Heinemann, Oxford, 2002, p. 530.
removed in vacuo at 120 °C. The yield was 95%. GPC: MMpica
=
1
= 1400 a.m.u. (72%), 600 a.m.u. (28%). H NMR (CDCl3), δ:
7.05—7.33 (m, 5 H, (C6H5CH2)(CH3)2Si); 1.98—2.23 (m, 2 H,
(C6H5CH2)(CH)3Si),); (m, 6 H, (CH3)2Si); 0.1—0.12 (m, 9 H,
(CH3)3Si).
Catalytic postꢀcondensation at the OH groups of copolymer.
The reaction was carried out by the addition of concentrated
sulfuric acid (1.36 g, 0.0139 mol) to the copolymer (136 g,
0.37 mol). The reaction mixture was stirred for 2 h, then diluted
with toluene until complete dissolution of the content, washed
Received December 26, 2014