2,2,4.4,6,6-Hexamethylcyclotrisiloxane

Sulfur Diimide Reduction. iV-Trichlorosilyldiaininosulfanes were prepared upon treatment of sulfur diimides with hexachloro-disilane (eq 9). Likewise, the corresponding IV-dichloromethyl-silyldiaminosulfanes resulted by substituting 1,2-dimethyl-1,1,2,2-tetrachlorodisilane for hexachlorodisilane. 

) Silicon Chemistry, Corey, J. Y Corey, E. R. Caspar, P. R, Eds. Ellis Horwood Chichester, 1987. (b) Organosilicon Compounds, Eaborn, C., Ed. Butterworth London, 1960. 

Handling, Storage, and Precautions hexamethylcyclotrisiloxane is a stable, crystalline solid that can be stored in a bottle without precaution for air and moisture exposure. 

A list of General Abbreviations appears on the front Endpapers 

Organolithium Reagents from Halogen-metal Exchange. 

---

C. (.Z)-l-(l-Heptenyl)-l,l-dimethylsilanol. A solution of 13.0 g (58 mmol) of (Z)-1 -iodo-1 -heptene in 50 mL of ether is placed in a flame-dried, three-necked, 300-mL, round-bottomed flask equipped with stirbar, septum, temperature probe, and N2 inlet. The solution is cooled to -72°C and a solution of n-BuLi in hexane (Note 4) (35.6 mL, 1.63M, 58 mmol) is then added by syringe over 15 min. The mixture is stirred at -72°C for 30 min and then a solution of 4.30 g (19.3 mmol) of hexamethylcyclotrisiloxane (Note 17) in 50 mL of ether is added over 15 min. The cooling bath is removed, and the reaction solution is allowed to warm to room temperature and stirred for 14 hr. The solution is then cooled to 0°C and 50 mL of water is slowly added to quench the reaction. The aqueous layer is separated and extracted with three 50-mL portions of diethyl ether. The combined organic phases are washed with 30 mL of water and two 30-mL portions of brine, dried over anhydrous MgS04, filtered, and concentrated by rotary evaporator and vacuum drying to give a crude product which is distilled to afford 7.34 g (73%) of (Z)-1 -(1 -heptcnyl)-1,1 -dimcthylsilanol as a colorless liquid, bp 54-55°C at 0.15 mm (lit.3 120°C at 0.9 mm) (Notes 18, 19). 

Hexamethylcyclotrisiloxane was purchased from Gelest Inc. and was used as received. 

Deuterated monomers (styrene, butadiene, oxirane, hexamethylcyclotrisiloxane)... 

Poly (dimethyl siloxane) obtained by anionic ring-opening polymerization of hexamethylcyclotrisiloxane (D3) can also be end-capped with vinylbenzyl bromide or other electrophiles, such as p. (chlorodimethylsilyl)styrene80). 

The identification of the structures responsible for D1 and D2 and their stabilities toward hydrolysis are further supported by investigations of the hydrolysis behavior of the corresponding isolated ring molecules, octamethylcyclotetrasiloxane (OMCT) and hexamethylcyclotrisiloxane (HMCT) (51.). OMCT is stable in aqueous environments, whereas HMCT hydrolyzes with a pseudo-first order rate constant 3.8 ( 0.4) x 10 3 min 1 (tt, 2 — 3.0 hours). This latter value is comparable to the rate constant for D2 hydrolysis, 5.2 ( 0.5) x 10 3 min"1 (t1/2 - 2.2 hours) and is 75x greater than the rate constant describing hydrolysis of unstrained, conventional a-Si02 (as estimated by extrapolation of the data in reference (52.). 

For example, in the case of intramolecularly base-stabilized silanone 4 it was trapped by excess hexamethylcyclotrisiloxane to give the corresponding insertion product 5 but isolated as a trimer 6 in the absence of such a trapping reagent (Scheme 2).17... 

Monomers. tetraethylsilicate (TES) and styrene were BDH AnalaR grade and hexamethylcyclotrisiloxane (HMCTS) was supplied by Aldrich. The styrene was distilled under reduced pressure from calcium hydrides prior to use and HMCTS sublimed under vacuum directly into the reaction vessel. 

Polydimethylsiloxane was prepared by the anionic polymerisation of hexamethylcyclotrisiloxane, in a solvent mixture of cyclohexane and THF (4 1 volume ratio), using n-butyllithium as the initiator. After a reaction period of 48 hr termination was effected by adding a small quantity of acetic acid. 

The analysis of methsuximide (I) is performed in carbon tetrachloride and of phensuximide (II) in 10% v/v dichloromethane in carbon tetrachloride. In this particular analysis hexamethylcyclotrisiloxane (III) is employed as an internal standard for (I) and (II) whereas the frequencies are referenced to usual tetra-methylsilane (TNS). 

The preparation proceeds in the following way A telechelic alcohol-functional PIB is first reacted with butyllithium in order to form an alcoholate-functional PIB dianion and the latter is then reacted with hexamethylcyclotrisiloxane to generate a living poly(dimeth-ylsiloxane) chain at the end groups of the PIB. In a final step, the remaining anionic ends are capped with trimethylchlorosilane or dimethyldichlorosilane. In this way a block copolymer, is obtained. The pressure sensitive adhesive exhibits (83) ... 

---