1693-44-3Relevant academic research and scientific papers
PROCESS FOR THE PRODUCTION OF CYCLOSILOXANES
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Paragraph 0021, (2013/04/10)
Embodiments of the invention are directed to the preparation of a discrete cyclosiloxane or a discrete mixture of cyclosiloxanes where a dihydroxysilane or dihydroxysiloxane condenses with a dihydrosilane or dihydroxysiloxane in the presence of a Lewis acid catalyst in a reaction phase including a solvent. The introduction of the dihydroxysilane or dihydroxysiloxane and dihydrosilane or dihydroxysiloxane is controlled such that the cyclocondensation occurs in a reaction phase that is dilute in the SiH and SiOH functionality permitting the isolation of the monocyclocondensation adduct in high yield with little higher molecular weight condensation products. In one embodiment of the invention 1,1-diphenyl-3,3,5,5-tetramethylcyclotrisiloxane is prepared in very high yield.
Silanones and silanethiones from the reactions of transient silylenes with oxiranes and thiiranes in solution. The direct detection of diphenylsilanethione
Kostina, Svetlana S.,Leigh, William J.
supporting information; experimental part, p. 4377 - 4388 (2011/06/11)
The transient silylenes SiMe2 and SiPh2 react with cyclohexene oxide (CHO), propylene oxide (PrO), and propylene sulfide (PrS) in hydrocarbon solvents to form products consistent with the formation of the corresponding transient silanones and silanethiones, respectively. Laser flash photolysis studies show that these reactions proceed via multistep sequences involving the intermediacy of the corresponding silylene-oxirane or -thiirane complexes, which are formed with rate constants close to the diffusion limit in all cases and exhibit UV absorption spectra similar to those of the corresponding complexes with the nonreactive O- and S-donors, tetrahydrofuran and tetrahydrothiophene. The SiMe2-PrO and SiPh2-PrO complexes both exhibit lifetimes of ca. 300 ns, and are longer-lived than the corresponding complexes with CHO, which are both in the range of 230-240 ns. On the other hand, the silylene-PrS complexes are considerably shorter-lived and vary with silyl substituent; the SiMe2-PrS complex decays with the excitation laser pulse (i.e., τ ≥ 25 ns), while the SiPh2-PrS complex exhibits τ = 48 ± 3 ns. The decay of the SiPh2-PrS complex affords a long-lived transient product exhibiting λ max ≈ 275 nm, which has been assigned to diphenylsilanethione (Ph2Si=S) on the basis of its second order decay kinetics and absolute rate constants for reaction with methanol, tert-butanol, acetic acid, and n-butyl amine, for which values in the range of 1.4 × 108 to 3.2 × 109 M-1 s-1 are reported. The experimental rate constants for decay of the SiMe2-epoxide and -PrS complexes indicate free energy barriers (ΔG?) of ca. 8.5 and ≥7.1 kcal mol-1 for the rate-determining steps leading to dimethylsilanone and -silanethione, respectively, which are compared to the results of DFT (B3LYP/6-311+G(d,p)) calculations of the reactions of SiH 2 and SiMe2 with oxirane and thiirane. The calculations predict a stepwise C-O cleavage mechanism involving singlet biradical intermediates for the silylene-oxirane complexes, and a concerted mechanism for silanethione formation from the silylene-thiirane complexes, in agreement with earlier ab initio studies of the SiH2-oxirane and -thiirane systems.
Electrochemical activation of diorganyl dialkoxysilanes for siloxane backbone extension
Keyrouz, Robert,Jouikov, Viatcheslav
, p. 902 - 904 (2007/10/03)
The reaction of diorganyl dialkoxysilanes PhRSi(OAlk)2 (R = Ph, vinyl, OMe; Alk = Me, Et) with electrochemically reduced forms of oxygen provides reactive intermediates that insert into hexamethyldisiloxane or permethyl cyclosiloxanes, D3
DEHYDROCONDENSATION OF ORGANIC HYDROSILANES WITH SILANOLS. PART I. KINETICS AND MECHANISM OF THE REACTION IN DIMETHYLFORMAMIDE
Chrusciel, Jerzy,Lasocki, Zygmunt
, p. 113 - 120 (2007/10/02)
Kinetics of dehydrocondensation of organic hydrosilanes with silanols in DMF and in presence of zinc and cadmium halogenides has been studied.The reactivities of series of hydrosilanes and hydrosiloxanes were determined.Activation parameters of the reaction and catalytic activities of the catalysts were determined and shown to be consistent with the mechanism which had been earlier proposed basing on formal kinetics.
DEHYDROCONDENSATION OF ORGANIC HYDROSILANES WITH SILANOLS. PART II. EFFECT OF SILOXANE CHAIN LENGTH ON THE REACTIVITY OF SI-H END-GROUPS. THE SUBSTITUTION EFFECT
Chrusciel, Jerzy,Lasocki, Zygmunt
, p. 121 - 128 (2007/10/02)
It has been found that the reactivity of Si-H end-groups in the homologous series of α,-dihydropolidimethylsiloxanes H(Me2SiO)nSiMe2H in their reaction with diphenylsilanediol in DMF and in presence of ZnCl2 decreases for n changing from 1 to 3 and is stabilized for larger n.The substitution effect of a single Si-H group in 1,1,3,3-tetramethyldisiloxane by triphenylsilanol was determined from rate measurements of the reaction of the primary product of condensation: 1,1,3,3-tetramethyl-5,5,5-triphenyltrisiloxane, which was prepared independently.A kinetic model of non-equilibrium polycondensation proceeding with a single reactivity change of a functional group was devised and numerically checked.
