S. Varaprath / Journal of Organometallic Chemistry 572 (1999) 37–47
47
concentration. For obtaining an 100 ppm aqueous solu-
References
tion, 15 ul of 14C-Me2Si(OMe)2 was added to 100 ml of
pure water (milli-Q water) taken in a 4 oz teflon bottle.
The contents were stirred for 2 h to complete the
hydrolysis. The specific activity of the product was
determined to be 2.5 mCi ml−1. The radiochemical
purity as determined by HPLC was 95%.
[1] G. Koerner, M. Schulze, J. Weis (Eds.), Silicones: Chemistry
and Technology, Vulkan-Verlag, Essen, Germany, 1991.
[2] J.F. Hobson, Existing chemical testing for environmental fate
and effects under TSCA Section 4: a case study with oc-
tamethylcyclotetrasiloxane (OMCTS), Environ. Toxicol. Chem.
14 (1995) 1635.
[3] R. Grau, Octamethylcyclotetrasiloxane (OMCTS) prolonged
toxicity (14 days) to rainbow trout in a flow-through test.
TSCA Docket OPTS-42071B. Toxic substances Control Act
Public Docket Office, Washington, DC, 1991.
[4] J.V. Sousa, P.C. McNamara, A.E. Putt, et al., Effects of oc-
tamethyl-cyclotetrasiloxane (OMCTS) on fresh water and
marine organisms, Environ. Toxicol. Chem. 14 (1995) 1639.
[5] D.J. Kent, P.C. McNamara, A.E. Putt, J.F. Hobson, E.M.
Silberhorn, M. Eric, Octamethylcyclotetrasiloxane in aquatic
sediments: toxicity and risk assessment, Ecotoxicol. Environ.
Saf. 29 (1994) 372.
[6] P.H. Fackler, E. Dionne, D.A. Hartlet, J.L. Hamelink, Biocon-
centration by fish of a highly volatile silicone compound in a
totally enclosed aquatic exposure system, Environ. Toxicol.
Chem. 14 (1995) 1649.
[7] Interagency Testing Agency. 1984. Fifteenth report to the ad-
ministrator. TSCA docket OPTS-42071A (1988). Fed. Reg.
49:46931–46949.
[8] R.G. Lehmann, S. Varaprath, C.L. Frye, Fate of silicone
degradation products (silanols) in soil, Environ. Toxicol. Chem.
13 (1994) 1753.
[9] J.C. Carpenter, J.A. Cella, S.B. Dorn, A study of the degrada-
tion of polydimethylsiloxanes on soil, Environ. Sci. Technol. 29
(1995) 864.
[10] R.G. Lehmann, S. Varaprath, R.B. Annelin, J. Arndt, Degra-
dation of silicone polymer on a variety of soils, Environ. Toxi-
col. Chem. 14 (1995) 1299.
[11] R.G. Lehmann, S. Varaprath, C.L. Frye, Degradation of sili-
conepolymers in soil, Environ. Toxicol. Chem. 13 (1994) 1061.
[12] R.G. Lehmann, C.L. Frye, D.A. Tolle, T.C. Zwick, Fate of
sludge applied silicones in agricultural soil microcosms, Water
Air Soil Pollut. 87 (1996) 231.
3.9. Synthesis of polydimethylsiloxane polymers
3.9.1. C-14 Labeled PDMS of 350 cSt
14C-D4 (25 mCi, of specific activity 1.48 mCi
mmol−1, purchased from Wizard Laboratories, West
Sacramento, CA) was placed in a 200 ml, one-necked
round-bottom flask. Pure D4 was added to the flask in
an amount to make the total weight of D4 to 50.0 g.
MD3M (1.625 g) and Amberlyst-15 (0.665 g) were then
placed in the flask. The flask was equipped with a water
condenser. The top of the condenser was in turn fitted
with a ‘Drierite’ moisture trap. The contents of the
flask were gently stirred using a magnetic stir bar and
the flask was heated for 24 h in an oil bath kept at
100°C. Heating was stopped at the end of this period
and the flask cooled to ambient temperature.
The viscous fluid in the flask was diluted with 60 ml
of reagent grade dichloromethane. and filtered through
a Whatman c1 filter paper to remove the solid acid
catalyst. The filtrate was collected into a clean 250 ml
flask. The original flask and the filter paper were thor-
oughly rinsed with fresh solvent to insure complete
transfer of the PDMS fluid.
Most of the volatiles were removed using a rotary
evaporator at 90°C under aspirator pressure (60–80
mmHg). Removal of the remaining volatiles was ac-
complished by low pressure distillation at 150°C, 0.01
mmHg for 48 h. At the end of this period, the distilla-
tion was stopped and the flask cooled to r.t. The
product, obtained as a clear fluid, weighed 45 g (87%
yield). The specific activity of the product was deter-
mined to be 0.52 mCi g−1. and the viscosity was
362.490.21 cSt.
[13] S. Varaprath, K.L. Salyers, K. Plotzke, S. M. Nanavati, Anal.
Biochem. 1998 (accepted for publication).
[14] Y. Nagai, K. Yamazaki, I. Shiojima, N. Kobori, M. Hayashi,
J. Organomet. Chem. 9 (1967) 21.
[15] Joel D. citron, James E. Lyons, Leo Sommer, J. Org. Chem. 34
(1969) 638.
[16] N.N. Sokolov, K.A. Andrianov, S.M. Akimova, Zhurnal Ob-
shchei Khimii (English trans.) 26 (1956) 933, pp. 1061–1063.
[17] K.A. Andrianov, A.I. Chernyavskii, N.N. Makarava, Synthesis
of bis [organo-cyclotri(tetra,penta)siloxy]polydimethylsiloxane,
Izv. Akad. SSSR Ser. Khim. 8 (1979) 1835.
3.10. C-14 Labeled PDMS of 1000 cSt
The 14C-labeled 1000 cSt PDMS was prepared fol-
lowing the procedure described for 350 cSt PDMS fluid
with the following exception. At the end of the reac-
tion, pentane rather than dichloromethane was used as
the diluent. The ingredients were as follows: 14C-D4
(1.14 g of specific activity 6.5 mCi mmol−1 from Wiz-
ard Laboratories, West Sacramento, CA) MD3M (1.34
g); unlabeled pure D4 (68.86 g); Amberlyst-15 (0.93 g).
The product was obtained in an 85% yield (60.3 g). The
specific activity was determined to be 0.302 mCi g−1
and the viscosity was 976.7 cSt.
[18] E.J. Hobbs, M.L. Keplinger, J.C. Calandra, Toxicity of poly-
dimethyl-siloxanes in certain environmental systems, Environ.
Res. 10 (1975) 397.
[19] R.J. Watts, S. Kong, C.S. Haling, L. Gearhart, C.L. Frye,
B.W. Vigon, Fate and effects of polydimethylsiloxanes on pilot
and bench-top activated sludge reactors and anaerobic/aerobic
digestors, Water Res. 29 (1995) 2405.
[20] Vladimir Bazant, Vaclav Chvalovsky, Jiri Rathousky,
Organosilicon Compounds, Academic Press, New York, 1965,
p. 42.
[21] J.A. Cella, J.C. Carpenter, Preparation of 14C-labeled dimethyl-
silane-1,1-diol, J. Label. Compd. Radiopharm. 34 (5) (1994)
427.
.