- A disiloxane equilibration approach to the preparation and characterization of 5,5'-(1,1,3,3-tetramethyldisiloxane-1,3-diyl)bisbicycloheptane-2,3-dicarboxylic anhydride
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The preparation of 5,5'-(1,1,3,3-tetramethyldisiloxane-1,3-diyl)bisbicycloheptene-2,3-dicarboxylic anhydride, 3, by a novel synthetic approach was found to be an effective method to isolate this disiloxane which is difficult to purify.The structure of the diastereomerically mixed product was confirmed by a combination of nuclear magnetic resonance spectroscopic and liquid chromatographic studies and correlated to the X-ray structure from the D,L-isomer.The hydrosilation of bicyclohept-5-ene-2,3-dicarboxylic anhydride 1 by 1,1,3,3-tetramethyldisiloxane and pentamethyldisiloxane is compared.
- Swint, S. A.,Buese, Mark A.
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- Kinetic Investigation of the Platinum-catalysed Hydrosilylation of Vinylsiloxanes with Hydrogensiloxanes
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A kinetic investigation of the platinum-catalysed hydrosilylation of monofunctional oligomeric vinylsiloxanes by monofunctional oligomeric hydrogensiloxanes was performed under stoichiometric conditions with use of quantitative 1H-NMR spectrometry.The reaction rate up to 50percent conversion can be expressed by v=k .During further hydrosilylation the kinetic changed to second order.No induction period was observed.A hydrogensiloxane with a dimethylsilyl end group gives much higher rates than a siloxane with a methylsiloxy group.The main reactions of all hydrosilylations, determined by GC-MS and 29Si-NMR, are β-additions.Less then 5percent α-products are obtained.
- Brand, Dagmar,Moretto, Hans-Heinrich,Schulze, Manfred,Wrobel, Dieter
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- Preparation method and application of trimethyl silicon alkoxide
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The invention discloses a preparation method and an application of trimethyl silicon alkoxide. The preparation method includes the preparation steps: placing hexamethyldisiloxane and potassium hydroxide into a 10L three-mouth flask; adding 10ml of alcohol preparations; performing heating reflux for 48 hours; dividing water by a water knockout trap; cooling, filtering and drying materials to obtain white solid potassium trimethylsilanolate. Inexpensive trimethyl silicon alkoxide (MM) in industrial production serves as a raw material, and the trimethyl silicon alkoxide and the potassium hydroxide are subjected to heating reflux reaction under various catalysts to prepare potassium trimethylsilanolate with high content. All the catalysts are beneficial to dissolution of the potassium hydroxide, and reaction is facilitated.
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Paragraph 0018
(2017/10/22)
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- 1,1,1,3,3,5,5-heptamethyltrisiloxane preparation method
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The present invention discloses a 1,1,1,3,3,5,5-heptamethyltrisiloxane preparation method, wherein 1,1,1,3,3,3-hexamethyldisiloxane and 1,1,3,3-tetramethyldisiloxane are subjected to co-hydrolysis for 1-4 h under catalysis of concentrated sulfuric acid to obtain 1,1,1,3,3-pentamethyldisiloxane, the 1,1,1,3,3-pentamethyldisiloxane and dimethyl dimethoxy silicane are subjected to co-hydrolysis for 1-3 h under catalysis of concentrated sulfuric acid, rectification is performed, and the distillate at a temperature of 135 DEG C is collected so as to obtain the 1,1,1,3,3,5,5-heptamethyltrisiloxane product. According to the present invention, the method has characteristics of strong target property, less by-product content in the product, and easy separation.
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Paragraph 0015; 0016
(2016/11/21)
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- Effect of catalyst structure on the reaction of α-methylstyrene with 1,1,3,3-tetramethyldisiloxane
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Reaction of α-methylstyrene with 1,1,3,3-tetramethyldisiloxane in the presence of the complexes of platinum(II), palladium(II) and rhodium(I) is explored. It is established that in the presence of platinum catalyst predominantly occurs hydrosilylation of α-methylstyrene leading to formation of β-adduct, on palladium catalysts proceeds reduction of α-methylstyrene, on rhodium catalysts both the processes take place. In the reaction mixture proceeds disproportion and dehydrocondensation of 1,1,3,3-tetramethyldisiloxane that leads to formation of long chain linear and cyclic siloxanes of general formula HMe2Si(OSiMe2) n H and (-OSiMe2-)m (n = 2-6, m = 3-7), respectively. Platinum catalysts promotes formation of linear siloxanes, while both rhodium and palladium catalysts afford linear and cyclic siloxanes as well. Structure of intermediate metallocomplexes is studied.
- De Vekki,Skvortsov
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p. 762 - 777
(2009/09/26)
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- Gas-phase reaction of free diethylsilylium ions with hexamethyldisiloxane
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The gas-phase reaction of diethylsilylium ions with hexamethyldisiloxane was studied by the radiochemical procedure. As in reactions with other nucleophiles, the degree of rearrangement of the diethylsilylium ion in the reaction with hexamethyldisiloxane correlates with the condensation energy. In contrast to the reaction of Et2SiT+ with dibutyl ether, in the reaction with hexamethyldisiloxane the labeled substrate is formed, which is due to isomerization of the trimethylsilyl substituent giving rise to a labile hydrogen atom. 2005 Pleiades Publishing, Inc.
- Kochina,Vrazhnov,Sinotova,Ignat'ev
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p. 708 - 710
(2007/10/03)
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- New route to permethylcyclosiloxanes
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A new method for preparing permethylcyclosiloxanes, based on reaction of 1,1,3,3-tetramethyldisiloxane with iodine (molar ratio 1:1) in inert organic solvents (alkanes, alkyl halides, benzene) is proposed. The products of the reaction react with ethoxytrimethylsilane and tetramethoxysilane in hexamethyldisiloxane to give respectively pentamethyldisiloxane and products of successive substitution of the methoxy groups in Si(OMe)4 by Me2SiHO. A probable scheme of their formation is discussed.
- Basenko,Klyba,Voronkov
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p. 1368 - 1370
(2007/10/03)
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- Symetrical hydroxyphenyl-s-triazine compositions
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The invention is concerned with compounds of formula I: STR1 which are useful as sun screening agents.
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- Reactions of lithium hydridosilylamides with carbonyl compounds and mixtures of carbonyl compounds and chlorotrimethylsilane
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The lithium hydridosilylamides Me2(H)SiN(Li)R (1: R = CMe3, 2: R = SiMe3) were allowed to react either with the non-enolizable carbonyl compounds CH2=C(Me)CHO, PhCHO and Ph2CO followed by trapping with chlorotrimethylsilane (A), or with mixtures of these carbonyl compounds and chlorotrimethylsilane (B). In the second case the course of the reactions is determined by the carbonyl compound. The composition of the reaction mixtures is nearly the same according to A and B. Main products in the reactions with the aldehydes are the corresponding imines R1CH=NR R1 = CH2=C(Me), Ph) 3, 4, 8, 9 formed by addition of the hydridosilylamides to the C=O group of the aldehydes and subsequent LiOSiMe2H elimination. Partial hydrosilylation of the aldehydes by the hydridosilanolate followed by the trimethylsilylation yields the alkoxydisiloxanes R1CH2OSiMe2OSiMe3 6, 11. In some cases 2 partially reacts under hydrosilylation to give the alkoxydisilazanes R1CH2OSiMe2NHSiMe3 7, 12. The hydrosilylation is the preferred reaction of 1 and 2 with benzophenone. The compounds Ph2CHOSiMe2NHR 13, 14 are obtained. This difference in the reaction behaviour of 1 and 2 towards the aldehydes and benzophenone is mainly due to steric reasons. Depending on the conditions the imines Ph2C=NR 20, 21 may be formed. Ph2CHOSiMe2OSiMe3 (22) is a secondary product of imine formation. In all reactions of 1 and 2 with the carbonyl compounds the corresponding alkoxysilanes R1CH2OSiMe3 (5: R1 = CH2=C(Me), 6: R1 = Ph) and Ph2CHOSiMe3 (15) are generated. Compounds resulting from a reaction of 1 and 2 with chlorotrimethylsilane are produced to minor extent, but only if the molar ratio of amide to carbonyl compounds is not greater than one. The formation of a silanimine intermediate in reaction according to B is not observed.
- Schneider, Jan,Popowski, Eckhard,Fuhrmann, Hans
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p. 663 - 672
(2007/10/03)
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- Hydrosilation of endo-cis-5-Norbornene-2,3-dicarboxylic Anhydride
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In hydrosilation of endo-cis-5-norbornene-2,3-dicarboxyIic anhydride with pentamethyldisiloxane and heptamethyltrisiloxane catalyzed by platinum(II) complexes, the mixed complexes with amino and sulfoxide ligands are the most active. The differences between the activities of the exo and endo isomers were explained on the basis of quantum chemical calculations indicating significant difference in the frontal orbitals of the exo and endo derivatives of norbornenedicarboxylic anhydride and the corresponding imides. A lower activity of the endo isomers is due to a change in the structure of the lowest unoccupied molecular orbital and its weak π-acceptor interaction with the transition metal atom in the course of the catalytic cycle.
- Trofimov,Skvortsov,Pashnova,Skvortsov
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p. 572 - 577
(2007/10/03)
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