- High-speed living polymerization of polar vinyl monomers by self-healing silylium catalysts
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This contribution describes the development and demonstration of the ambient-temperature, high-speed living polymerization of polar vinyl monomers (M) with a low silylium catalyst loading (≤ 0.05 mol % relative to M). The catalyst is generated in situ by protonation of a trialkylsilyl ketene acetal (RSKA) initiator (I) with a strong Bryonsted acid. The living character of the polymerization system has been demonstrated by several key lines of evidence, including the observed linear growth of the chain length as a function of monomer conversion at a given [M]/[I] ratio, near-precise polymer number-average molecular weight (Mn, controlled by the [M]/[I] ratio) with narrow molecular weight distributions (MWD), absence of an induction period and chain-termination reactions (as revealed by kinetics), readily achievable chain extension, and the successful synthesis of well-defined block copolymers. Fundamental steps of activation, initiation, propagation, and catalyst self-repair involved in this living polymerization system have been elucidated, chiefly featuring a propagation catalysis cycle consisting of a rate-limiting C-C bond formation step and fast release of the silylium catalyst to the incoming monomer. Effects of acid activator, catalyst and monomer structure, and reaction temperature on polymerization characteristics have also been examined. Among the three strong acids incorporating a weakly coordinating borate or a chiral disulfonimide anion, the oxonium acid [H(Et2O)2] + [B(C 6F5)4]- is the most effective activator, which spontaneously delivers the most active R3Si +, reaching a high catalyst turn-over frequency (TOF) of 6.0 x 103 h-1 for methyl methacrylate polymerization by Me 3Si+ or an exceptionally high TOF of 2.4 x 105 h-1 for n-butyl acrylate polymerization by iBu3Si +, in addition to its high (>90%) to quantitative efficiencies and a high degree of control over Mn, and MWD (1.07-1.12). An intriguing catalyst self-repair feature has also been demonstrated for the current living polymerization system.
- Zhang, Yuetao,Lay, Frank,Garcia-Garcia, Pilar,List, Benjamin,Chen, Eugene Y.-X.
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- Reaction of O(3P) with Hexamethyldisilane
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The title reaction has been investigated at room temperature in a discharge flow system and also by stationary Hg(3P1)-sensitized N2O photolysis experiments.By far the most important reaction is the insertion of O(3P) atoms into the Si-Si bond yielding a vibrationally excited hexamethyldisiloxane.The rate constant for this reaction has been measured to be (1.3 +/- 0.3) x 10-13 cm3 s-1.The vibrationally excited hexamethyldisiloxane could not be stabilized at pressures up to 1 bar, decomposing mainly by Si-C bond cleavage.A reaction mechanism is proposed to account for the observed products.
- Hoffmeyer, H.,Potzinger, P.,Reimann, B.
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- The role of the phase quasiequilibrium in the reaction system chlorotriorganosilane-water-acetone
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On the basis of analysis of product composition in the hydrolytic polycondensation (HPC) of chlorotriorganosilanes, the parameters of the kinetic and the diffusion field, the zone of the reaction, and the region of the conodes of the phase diagrams are determined.It is suggested that the conodes correspond to a phase quasiequilibrium, which defines the composition of the reaction products.The results of this investigation confirm the previously discovered features of HPC of dichloromethylphenylsilanes: the formation of the siloxane bond during the hydrolysis of chloroorganosilanes by water mainly occurs in the organic phase of the system and proceeds as the heterofunctional polycondensation of the reaction products with the starting chloroorganosilanes.The role of the phase quasiequilibrium consists of the creation of a field of reagent concentration, based on which one can control the composition of the reaction products. - Key words: quasiequilibrium; conodes; Gibbs phase diagram; hydrolysis; chloroorganosilanes; silanols; field of the reaction.
- Ivanov, P. V.,Maslova, V. I.,Mlakhovskaya, O. V.,Chernyshev, E. A.
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- CONDENSATION REACTIONS OF α-AMINO-ZINCENAMINES WITH ALDEHYDES; APPLICATION TO INDOLIZINES
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The zinc-enamine 1 is easy accessible via the reaction of Et2Zn with t-BuN=CHCH=Nt-Bu and is reactive towards aldehydes.The condensation reaction of 1 with 2-pyridine-carboxaldehyde results in the thermally instable zinc-aldolate 2b that subsequently rearranges to the indolizine 4.
- Wissing, Elmo,Havenith, Remco W. A.,Boersma, Jaap,Koten, Gerard van
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- Reaction of O(3P) with Trimethylsilane
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The title reaction has been investigated at room temperature in a discharge flow system as well as by stationary Hg(3P1) sensitized N2O photolysis experiments.O(3P) atoms abstract hydrogen from the silicon center with a rate constant of k(1) = (2.6 +/= 0.3)E-12 cm3s-1.Hydroxyl radicals formed in the primary step react in a second abstraction reaction to yield H2O with a rate constant larger than k(1) by a factor of about 20.The fate of trimethylsilyl radical, the other primary product, depends on the experimental conditions.In the flow system they combine with O and OH; the combination products decompose unimolecularly, yielding CH3 and CH4, respectively, and the common product (CH3)2SiO.In stationary photolyses they mainly abstract O from N2O to ultimately form (CH3)3SiOSi(CH3)3.In a separate static experiment a ratio of k(14)/k1/2(7) = 2.5E-12 cm3/2s-1/2 has been determined for oxygen abstraction of trimethylsilyl radicals from N2O vs. combination of two trimethylsilyl radicals.The rate constant of N(4S) with trimethylsilane has been measured in the flow system to be k(2) = (2.6 +/= 0.8)E-14 cm3s-1.
- Hoffmeyer, H.,Horie, O.,Potzinger, P.,Reimann, B.
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- Trimethylsilyl group migration in the Criegee intermediate of gas-phase ozonolysis of trimethylsilylethenes
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GC, GC/MIS and GC/FTIR analyses of the final products of ozonolysis of trimethylsilylethene and trans-1,3-bis(trimethylsilyl)ethene reveal that the ester channel of decomposition of the Criegee intermediate takes place exclusively via migration of Me
- Fajgar, Radek,Pola, Josef
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- Enzyme mediated silicon-oxygen bond formation; The use of Rhizopus oryzae lipase, lysozyme and phytase under mild conditions
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The potential for expanding the variety of enzymic methods for siloxane bond formation is explored. Three enzymes, Rhizopus oryzae lipase (ROL), lysozyme and phytase are reported to catalyse the condensation of the model compound, trimethylsilanol, formed in situ from trimethylethoxysilane, to produce hexamethyldisiloxane in aqueous media at 25 °C and pH 7. Thermal denaturation and reactant inhibition experiments were conducted to better understand the catalytic role of these enzyme candidates. It was found that enzyme activities were significantly reduced following thermal treatment, suggesting a potential key-role of the enzyme active sites in the catalysis. Similarly, residue-specific modification of the key-amino acids believed to participate in the ROL catalysis also had a significant effect on the silicon bio-catalysis, indicating that the catalytic triad of the lipase may be involved during the enzyme-mediated formation of the silicon-oxygen bond. E. coli phytase was found to be particularly effective at catalysing the condensation of trimethylsilanol in a predominantly organic medium consisting of 95% acetonitrile and 5% water. Whereas the use of enzymes in silicon chemistry is still very much a developing and frontier activity, the results presented herein give some grounds for optimism that the variety of enzyme mediated reactions will continue to increase and may one day become a routine element in the portfolio of the synthetic silicon chemist. The Royal Society of Chemistry.
- Abbate, Vincenzo,Bassindale, Alan R.,Brandstadt, Kurt F.,Lawson, Rachel,Taylor, Peter G.
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- DEOXYMETALATION REACTIONS. THE MECHANISMS OF DEOXYSILYLATION OF MONO-TRIMETHYLSILYL-AND BIS-TRIMETHYLSILYL-SUBSTITUTED ALCOHOLS AND A COMPARISON TO THE MECHANISM OF DEOXYSTANNYLATION AND DEOXYPLUMBYLATION
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The relative rates of acid-catalyzed deoxysilylation of 2-trimethylsilyl-1-hydroxyethane, 4, 1-trimethylsilyl-2-hydroxypropane, 5, 1,3-bis(trimethylsilyl)-2-hydroxypropane, 6, and 1-trimethylsilyl-2-methyl-2-hydroxypropane, 7, were found to be 1 : 103.30 : 105.92 : 106.77, respectively, in 9 vol percent aqueous-methanol at 40 deg C.These rates are directly proportional to the sum of the ?+ constants of the substituents on the carbon bearing the nucleofuge (ρ+ = -11).The additive rate-accelerating effect of two trimethylsilyl groups requires equal conjugativen bystabilization by each trimethylsilyl group, and a mechanism involving a hyperconjugatively-stabilized carbocation intermediate is proposed.In contrast, the deoxymetalation reactions of the triphenyltin-, triphenyllead-, and iodomercury-analogs exhibit very different structure-reactivity relationships and have been described as proceeding through concerted E2-like or bridged-ion mechanisms.These mechanistic regimes are reconciled by considering the conjugative interactions, electrofugalities and nucleophilic solvent assistance at the organometal-leaving groups in terms of Thornton's Reacting Bond Rules.This analysis suggests a spectrum of merging mechanisms, the acid-catalyzed deoxysilylation representing one extreme, the E1M (carbocation intermediate) mechanism and the other Group IV deoxymetalation reactions more nearly concerted E2M-paths.
- Davis, Dennis D.,Jacocks, Henry M.
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- A Quantitative Scale for the Structural Effect on Reactivity toward Nucleophilic Displacement at Silicon
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The rates of solvolysis for forty different triorganochlorosilanes have been measured in 89 molpercent aqueous dioxane at 25 deg C; the logarithmic rates relative to that for trimethylchlorosilane, log krel = log 1R2R3SiCl)/k(Me3SiCl)>, provide a quantitative scale for the structural effect of various silyl groups on the reactivity toward nucleophilic displacement at silicon, ranging from 1.99 for HSiMe2 to -6.89 for t-BuSiPh2 groups.
- Shimizu, Nobujiro,Takesue, Naohide,Yamamoto, Akiko,Tsutsumi, Toru,Yasuhara, Sigefumi,Tsuno, Yuho
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- Sodiumoxy(aminopropyl)alkoxysilanes - AB2 type monomers for the synthesis of hyperbranched poly(aminopropyl)alkoxysiloxanes and their derivatives
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Based on commercially available aminopropyltrialkoxysilanes, new monosodium salts of organoalkoxysilanes (sodiumoxoaminopropyldialkoxysilanes) with two types of chemically independent functional -ONa and -OAlk groups at the silicon atom were synthesized and characterized. The sodiumoxoaminopropyldialkoxysilanes obtained can be regarded as AB2-type monomers - promising reagents for providing controlled polycondensation and production of functional organosilicon polymers with controlled molecular architectures. Subsequently, polyaminopropylsiloxanes with hyperbranched molecular architectures were obtained by heterofunctional polycondensation of the corresponding AB2-type monosodiumoxoorganodialkoxysilanes. The structures synthesized were characterized using 29Si NMR, 1H NMR, GPC and elemental analyses. The hyperbranched polymer matrices obtained containing aminopropyl organic radicals showed the ability to stabilize silver nanoparticles.
- Migulin, Dmitry,Milenin, Sergey,Cherkaev, Georgy,Svidchenko, Evgeniya,Surin, Nikolay,Muzafarov, Aziz
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- Synthesis of methyl(1-aminophosphonate)siloxane oligomers
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A synthesis of 1-aminophosphonate derivative of methylsiloxane oligomer was developed. A methodology of the introduction of 1-aminophosphonate fragment not only into the stable siloxane structures, but also into hydrolytically unstable alkoxyfunctional organosilicon compounds was suggested.
- Khairova,Milenin,Cherkaev,Stoikov,Muzafarov
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- Catalytic Dehydrocoupling of Silane by a Homogenous Rhodium Complex with Water
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Organosilicon hydrides are oxidized to the corresponding silanols in high yield in a homogenous phase in the presence of a small amount of water and a catalytic amount of a rhodium complex.
- Shi, Min,Nicholas, Kenneth M.
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- Spontaneous reduction and dispersion of graphene nano-platelets with in situ synthesized hydrazine assisted by hexamethyldisilazane
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The environmentally friendly reduction and a solution processability of chemically modified graphene nanosheets are most important for their applications. Here we report for the first time that in situ synthesis of hydrazine and spontaneous reduction of g
- Han, Joong Tark,Jang, Jeong In,Jeong, Bo Hwa,Kim, Beom Joon,Jeong, Seung Yol,Jeong, Hee Jin,Cho, Jeong Ho,Lee, Geon-Woong
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- The Reaction between Sulfur Dioxide and Hexamethyldisilazane. 3. The Characterization of Ammonium (Trimethylsilyl)sulfite
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The reaction between ((CH3)3Si)2NH and SO2 results in the formation of an anionic solid with empirical formula NH4(CH3)3SiOSO2 which readily "sublimes" at ambient temperature.Although (trimethylsilyl)ammonium bisulfite is a logical choice for a molecular formula, IR, NMR, and XPS data rule out the presence of RNH3+ and HSO3- ions.These data, along with a consideration of the solution behavior of this unique material, provide strong evidence that the substance is ammonium (trimethylsilyl)sulfite, with the silicon bonded to oxygen rather than sulfur.
- Bennett, D. W.,Spicer, L. D.
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- The low temperature crystal structure of trimethylsilanol
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A preparation of trimethylsilanol by hydrolysis of bis(trimethylsilyl)carbonate in diethylether at -20 °C is reported. At -80 °C, the crystals are monoclinic, space group P21/c, Z = 12 with cell dimensions a = 996.0(2) pm, b = 1730.2(3) pm, c = 1122.9(2) pm, β = 96,61(3)°. There are three independent Me3SiOH units with a slightly distorted tetrahedral C3SiO core structure.
- Minkwitz, Rolf,Schneider, Stefan
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- 2-Selenophenethiol and 5-methylthio-2-selenophenethiol: Synthesis and autoconversions
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Selenophenethiols have been synthesized by a modified organolithium method. The structures of the products were established by their autothiylation and reaction with phenylhydrazine. 1997 Plenum Publishing Corporation.
- Vvedenskii,Shtefan,Malyushenko,Shilkin
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- Interactions of hexachlorodiphosphazenium ion with an alcohol and with some silicon-oxygen reagents and their role in the catalysis of polycondensation in silanol-alkoxysilane systems
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Condensation reactions of trimethylethoxysilane (MOEt) and pentamethyldisiloxanol in n-heptane catalysed by hexachloro-1λ-diphosphaza-1-enium salts were studied. Although the substrate conversion vs. time dependences point to domination by heterofunctional condensation, the process is more complex. Homofunctional condensation as well as fast consecutive hydrolysis and ethanolysis strongly contribute to the overall process. Results of kinetic studies point to inhibition of these component reactions by an excess of MOEt. Interactions of the hexachloro-1λ-diphosphaza-1-enium salts with MOEt, ethanol and silanol were studied by 31P NMR. It was demonstrated that a fast substitution reaction of chloride by ethoxy group takes place when ethanol or ethoxysilane is introduced into solutions of hexachlorodiphosphazenium salts. This process is responsible for the decrease in condensation activity of the catalyst.
- Chojnowski, Julian,Cypryk, Marek,Fortuniak, Witold,Kazmierski, Krzysztof,Taylor, Richard G.
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- Disproportionation of oligodimethylsiloxanols in the presence of a protic acid in dioxane
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The kinetics of the acid-catalyzed disproportionation of α,ω-dihydroxyoligodimethylsiloxanes HOnH, n = 2, 5, and their analogues having one hydroxyl function replaced by methyl MenH, n = 2, 5, were studied in dioxane in the presence of water.The formation of the primary disproportionation products was monitored by gas-liquid chromatography.The reaction in dioxane solution can compete with the condensation process only in the presence of water.It is of first order with respect to the substrate, catalyst, and water.The results are interpreted in terms of a stepwise mechanism involving rate determining cleavage of the terminal siloxane unit by water, followed by condensation of transiently-formed dimethylsilanediol with the substrate.The unzipping mechansim involving the dimethylsilanediol intermediate is suggested to operate in hydrolytic cleavage of polydimethylsiloxane exposed to water or water vapour.
- Cypryk, M.,Rubinsztajn, S.,Chojnowski, J.
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- Atmospheric degradation of volatile methyl-silicon compounds
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The current widespread use of poly(dimethylsiloxane)s (PDMS) in a broad range of applications leads to their release into soil environments where they degrade to monomeric products, primarily dimethylsilanediol, most of which enter the atmosphere by volatilization. The major degradation pathway of volatile organosilicon compounds in the atmosphere is expected to be a reaction with hydroxyl (OH) radicals. In this work, the kinetics of the gas- phase reactions of dimethylsilanediol, trimethylsilanol, and tetramethylsilane with the OH radical were measured using a relative rate method which employed the N2H4 + O3 reaction as a nonphotolytic source of OH radicals, with analysis by Fourier transform infrared (FT-IR) spectroscopy in a 5870 L chamber. The measured values of the OH radical reaction rate constants (cm3 molecule-1 s-1) at 298 ± 2 K are as follows: dimethylsilanediol, (8.1 ± 1.0) x 10-13; trimethylsilanol, (7.2 ± 0.8) x 10-13; and tetramethylsilane, (8.5 ± 0.9) x 10-13. These values lead to an estimate of tropospheric lifetimes with respect to reaction with the OH radical of ca. 15 days for these organosilicon compounds. FT-IR spectroscopy and atmospheric pressure ionization mass spectrometry (API-MS) were employed to analyze the products of OH radical- and Cl atom-initiated photooxidations of dimethylsilanediol and trimethylsilanol. Infrared signatures of the probable formate ester intermediate products from both silanols were detected. API-MS analyses indicated the formation of methylsilanetriol from dimethylsilanediol, of both dimethylsilanediol and methylsilanetriol from trimethylsilanol, and of the corresponding intermediate formate esters. Possible reaction mechanisms are discussed. The current widespread use of poly(dimethylsiloxane)s (PDMS) in a broad range of applications leads to their release into soil environments where they degrade to monomeric products, primarily dimethylsilanediol, most of which enter the atmosphere by volatilization. The major degradation pathway of volatile organosilicon compounds in the atmosphere is expected to be a reaction with hydroxyl (OH) radicals. In this work, the kinetics of the gas-phase reactions of dimethylsilanediol, trimethylsilanol, and tetramethylsilane with the OH radical were measured using a relative rate method which employed the N2H4 + O3 reaction as a nonphotolytic source of OH radicals, with analysis by Fourier transform infrared (FT-IR) spectroscopy in a 5870 L chamber. The measured values of the OH radical reaction rate constants (cm3 molecule-1 s-1) at 298 ± 2 K are as follows: dimethylsilanediol, (8.1 ± 1.0) × 10-13; trimethylsilanol, (7.2 ± 0.8) × 1013; and tetramethylsilane, (8.5 ± 0.9) × 10-13. These values lead to an estimate of tropospheric lifetimes with respect to reaction with the OH radical of ca. 15 days for these organosilicon compounds. FT-IR spectroscopy and atmospheric pressure ionization mass spectrometry (API-MS) were employed to analyze the products of OH radical- and Cl atom-initiated photooxidations of dimethylsilanediol and trimethylsilanol. Infrared signatures of the probable formate ester intermediate products from both silanols were detected. API-MS analyses indicated the formation of methylsilanetriol from dimethylsilanediol, of both dimethylsilanediol and methylsilanetriol from trimethylsilanol, and of the corresponding intermediate formate esters. Possible reaction mechanisms are discussed.
- Tuazon, Ernesto C.,Aschmann, Sara M.,Atkinson, Roger
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- Proton-Coupled Electron Transfer Enables Tandem Radical Relay for Asymmetric Copper-Catalyzed Phosphinoylcyanation of Styrenes
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A tandem radical relay strategy was realized for the first Cu(I)-catalyzed enantioselective phosphinocyanation of styrenes. In this reaction, tBuOOSiMe3 generated in situ from tBuOOH serves as a radical initiator to trigger t-butoxy radical production upon oxidization of L?Cu(I) species via proton-coupled-electron transfer (PCET) pathway, which leads to sequential phosphinoyl radical and benzyl radical formations. The resultant β-cyanodiarylphosphine oxides could be easily converted to a series of chiral ?-amino phosphine ligands.
- Zhang, Guoyu,Fu, Liang,Chen, Pinhong,Zou, Jianping,Liu, Guosheng
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- The hydroxyl radical reaction rate constants and atmospheric reaction products of three siloxanes
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The relative rate technique has been used to measure the hydroxyl radical (OH) reaction rate constant of hexamethyldisiloxane (MM, (CH3)3Si-O-Si(CH3)3), octamethyltrisiloxane (MDM, (CH3)3Si-O-Si(CH3)2-O-Si(CH 3)3), and decamethyltetrasiloxane (MD2M, (CH3)3Si-O-Si(CH3)2-O-Si(CH 3)2-O-Si(CH3)3). Hexamethyldisiloxane, octamethyltrisiloxane, and decamethyltetrasiloxane react with OH with bimolecular rate constants of 1.32 ± 0.05 × 10-12 cm3molecule-1s-1, 1.83 ± 0.09 × 10-12 cm3 molecule-1, and 2.66 ±0.13 × 10-12 cm3molecule-1s-1, respectively. Investigation of the OH + siloxane reaction products yielded trimethylsilanol, pentamethyldisiloxanol, heptamethyltetrasiloxanol, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and other compounds. Several of these products have not been reported before because these siloxanes and the proposed reaction mechanisms yielding these products are complicated. Some unusual cyclic siloxane products were observed and their formation pathways are discussed in light of current understanding of siloxane atmospheric chemistry.
- Markgraf, Stewart J.,Wells
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- Influence of macroscopic factors on the composition of the products of cohydrolysis of triorganochlorosilanes
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The composition of the products of heterogeneous cohydrolysis of trimethyl- and dimethylphenylchlorosilanes by excess aqueous ammonia (4-5% solution) is determined by the regime of heterofunctional condensation of the initial chlorosilanes with the products of their hydrolysis, triorganosilanols. In a diffusion regime, hexaorganodisiloxanes are formed because of the limited possibility of removing silanols from the reaction zone, while silanols are predominantly formed in a kinetic regime. The influence of the nature of the solvent and surfactant and the intensity of stirring of the reaction mixture on the composition of the final products of hydrolytic cocondensation of triorganochlorosilanes is considered.
- Ivanov,Mlakhovskaya,Chernyshev,Kostikova,Mozzhukhin,Buzyreva
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- Copper-Phosphido Intermediates in Cu(IPr)-Catalyzed Synthesis of 1-Phosphapyracenes via Tandem Alkylation/Arylation of Primary Phosphines
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Tandem alkylation/arylation of primary phosphines PH2R (R = Ph, Cy, Fc, FcCH2; Fc = ferrocenyl) with 5-bromo-6-chloromethylacenaphthene (1) and 2 equiv of NaOSiMe3 using the catalyst precursor Cu(IPr)(Cl) gave a series of 1-phosphapyracenes (R-PyraPhos, 2a-d), which were isolated as borane adducts 3a-d. Similar reactions of the chiral air-stable primary phosphines PH2Ar? (Ar? = (S)-binaphthyl (4), (R)-MeO-binaphthyl (5)) to yield 2e,f and 3e,f were diastereoselective (dr = 2:1 and 1.2:1, respectively), and chromatography gave a highly enriched sample of one diastereomer of 3f. The mechanism of catalysis was investigated by NMR monitoring and independent syntheses of potential intermediates. The phosphido complexes Cu(IPr)(PHAr′) (Ar′ = Ph, (R)-MeO-binaphthyl) were generated in equilibrium mixtures, along with Me3SiOH, from Cu(IPr)(OSiMe3) and PH2Ar′. They reacted with benzyl chloride 1 to yield Cu(IPr)(Cl) and the secondary phosphines PHAr′(CH2Ar) (Ar = Br-acenaphthyl); addition of NaOSiMe3 yielded PyraPhos derivatives 2a,f. Deprotonation of the cations [Cu(IPr)(PHAr′CH2Ar)][OTf] (Ar′ = Ph, (R)-MeO-binaphthyl) was investigated as a route to the secondary phosphido complexes Cu(IPr)(PAr′CH2Ar) (13). We propose that C-Br oxidative addition in the Cu(I)-phosphido intermediates 13 followed by P-C reductive elimination from Cu(III)-phosphido complexes forms the PyraPhos ring, with diastereoselection arising from rapid pyramidal inversion of Cu-phosphido groups.
- Wang, Ge,Gibbons, Sarah K.,Glueck, David S.,Sibbald, Connor,Fleming, James T.,Higham, Lee J.,Rheingold, Arnold L.
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- Direct growth of crystalline triazine-based graphdiyne using surface-assisted deprotection-polymerisation
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Graphdiyne polymers have interesting electronic properties due to their π-conjugated structure and modular composition. Most of the known synthetic pathways for graphdiyne polymers yield amorphous solids because the irreversible formation of carbon-carbon bonds proceeds under kinetic control and because of defects introduced by the inherent chemical lability of terminal alkyne bonds in the monomers. Here, we present a one-pot surface-assisted deprotection/polymerisation protocol for the synthesis of crystalline graphdiynes over a copper surface starting with stable trimethylsilylated alkyne monomers. In comparison to conventional polymerisation protocols, our method yields large-area crystalline thin graphdiyne films and, at the same time, minimises detrimental effects on the monomers like oxidation or cyclotrimerisation side reactions typically associated with terminal alkynes. A detailed study of the reaction mechanism reveals that the deprotection and polymerisation of the monomer is promoted by Cu(ii) oxide/hydroxide species on the as-received copper surface. These findings pave the way for the scalable synthesis of crystalline graphdiyne-based materials as cohesive thin films.
- Amsalem, Patrick,Bojdys, Michael J.,Burmeister, David,Huang, Jieyang,Kass, Dustin,Koch, Norbert,Kulkarni, Ranjit,Müller, Johannes,Martin, Andréa,Trunk, Matthias
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p. 12661 - 12666
(2021/10/19)
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- Silanol Compound, Composition, and Method for Producing Silanol Compound
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The purpose of the present invention is to provide silanol compounds that can be used as raw materials of siloxane compounds and the like, and a composition of the silanol compounds, as well as to provide a production method that makes it possible to produce silanol compounds at excellent yield. A composition comprising 5 mass % to 100 mass % of a silanol compound represented by Formulas (A) to (C) can be prepared by devising to produce silanol compounds under water-free conditions, to produce silanol compounds in a solvent having the effect of suppressing the condensation of silanol compounds, and to perform other such processes, the composition being able to be used as a raw material or the like of siloxane compounds because the silanol compounds can be stably present in the resulting composition.
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Paragraph 0216; 0217
(2017/07/14)
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- Chemistry of phosphorus ylides: Part 44 reaction of 1-trimethylsilyl-1H-imidazole with phosphorus reagents. A convenient synthesis of phosphorus silyl imidazoles
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The reaction of 1-trimethylsilyl-1H-imidazole with nucleophilic active phosphacumulenes afforded imidazole silyl phosphoranylidenes or imidazole phosphoranylidenes according to the reaction conditions. The reaction of hexaphenylcarbodiphosphorane with 1-trimethylsilyl-1H-imidazole resulted in the formation of silyl phosphoranylidene phosphoranyl imidazole, silyl phosphoranylidene imidazole and triphenylphosphane. Moreover, Lawesson and Japanese reagents afforded imidazole phosphinothioic thioanhydrides.
- El-Hussieny, Marwa,Abd-El-Maksoud, Mansoura Ali,Maigali, Soher Said,Soliman, Fouad Mohamed
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p. 265 - 268
(2016/07/06)
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- Reactions of hydroxyl-containing compounds with tert-butyl hydroperoxide in the presence of chromium tetra-tert-butoxide
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Primary and secondary aliphatic, alkylaromatic, cyclic, and organoelement alcohols are efficiently oxidized by tert-butyl hydroperoxide in the presence of both equimolar and catalytic quantities of chromium tetra-tert-butoxide (C6H6, 20°C). α-Diols containing tertiary hydroxyl groups interact with this system via oxidative splitting of the carbon scaffold. The oxidation includes the stages of formation and decomposition of chromium-containing peroxy compounds. Further transformations of the carbonyl compounds depend on the structure of radicals in the molecules.
- Stepovik,Zaburdaeva,Fukin,Karaghiosoff
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p. 2547 - 2559
(2015/12/30)
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- Reaction of Carbodiimides with trifluoromethanesulfonic acid
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Carbodiimides RN=C=NR (R = i-Pr, c-C6H11, Ph) react with trifluoromethanesulfonic acid with successive formation of O-triflyl isoureas RNHC(OTf)=NR, the isomeric N-triflyl ureas RN(Tf)C(O)NHR, and symmetrically substituted ureas RNHC
- Tolstikova,Shainyan,Chipanina
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p. 1853 - 1858
(2014/01/06)
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- PROCESS FOR THE SYNTHESIS OF ALKYL PHOSPHINIC ACIDS BY INITIATION OF AN AMINE AND AN AMINEOXIDE
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The present invention relates toa new process for the synthesis of alkyl phosphinic acids, and more particularly to a coupling reaction between an alkylhalide and a hypophosphorous acid derivative in the presence of an amine and an amineoxide.
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Page/Page column 13-16
(2009/01/20)
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- PROCESS FOR THE SYNTHESIS OF ALKYL PHOSPHINIC ACIDS BY INITIATION OF AN AMINE AND AN AMINEOXIDE
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The present invention relates to a new process for the synthesis of alkyl phosphinic acids, and more particularly to a coupling reaction between an alkylhalide and a hypophosphorous acid derivative in the presence of an amine and an amineoxide.
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Page/Page column 11-14
(2009/01/20)
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- Efficient and facile Ar-Si bond cleavage by montmorillonite KSF: Synthetic and mechanistic aspects of solvent-free protodesilylation studied by solution and solid-state MAS NMR
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(Chemical Equation Presented) A facile and efficient method for the cleavage of the Ar-Si bond of various aryl trimethyl silanes is described. When adsorbed on montmorillonite KSF (mont KSF), these aryl-silanes readily undergo a solvent-free protodesilylation to the corresponding arenes at room temperature in excellent yields. This approach seems to be superior to the traditional mild methods (i.e., desilylation by TFA, TBAF, CsF), in terms of reaction yield, rate, and environmentally benign conditions. Some mechanistic studies using both solution and solid-state magic-angle spinning (SS MAS) 1H NMR are also presented.
- Zafrani, Yossi,Gershonov, Eytan,Columbus, Ishay
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p. 7014 - 7017
(2008/02/11)
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- STEREOSELECTIVE SYNTHESIS OF 3,4-DISUBSTITUTED CYCLOPENTANONES AND RELATED COMPOUNDS
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Methods and materials for preparing optically active 3,4-disubstituted cyclopentanones are disclosed. The method includes hydrolyzing one or more compounds represented by Formula (13), or removing an ester moiety from a compound represented by Formula (18).
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Page/Page column 37-38; 53-54
(2010/11/25)
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- Unprecedented 1,4-stannatropy: Effective generation of azomethine ylides as nitrile ylide equivalents from N-(stannylmethyl)thioamides
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Generation and cycloaddition of less- or non-stabilized azomethine ylides, or nitrile ylide equivalents, via unprecedented 1,4-stannatropy of N-(tributylstannylmethyl)thioamides were achieved. The reactions with dipolarophiles, such as electron-deficient alkenes and alkynes, afforded corresponding pyrrolidine and pyrrole derivatives effectively. The Royal Society of Chemistry 2006.
- Komatsu, Mitsuo,Kasano, Yukihiro,Yonemori, Jin-Ichi,Oderaotoshi, Yoji,Minakata, Satoshi
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p. 526 - 528
(2008/02/05)
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- Experimental determination of the conformational free energies (A values) of fluorinated substituents in cyclohexane by dynamic 19F NMR spectroscopy. Part 2. Extension to fluoromethyl, difluoromethyl, pentafluoroethyl, trifluoromethylthio and trifluoromethoxy groups
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The synthesis of monosubstituted and 1,4-substituted cyclohexanes bearing one of the title groups is described. The conformational analysis of these compounds was studied by 19F NMR spectroscopy at various temperatures. Chemical shifts for each conformer above the coalescence temperature were obtained by binomial regression from low temperature values, allowing the high precision determination of the equilibrium constants, and the corresponding thermodynamic parameters (ΔG°, ΔH°, ΔS°) of the fluorinated substituents. For A values (-ΔG°298K), the following averaged data were obtained: 1.59 (CFH2), 1.85 (CF2H), 2.67 (C2F5), 0.79 (OCF3) and 1.18 (SCF3) [in kcal mol-1]. the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2006.
- Carcenac, Yvan,Tordeux, Marc,Wakselman, Claude,Diter, Patrick
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p. 447 - 457
(2007/10/03)
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- STABLE PHARMACEUTICAL COMPOSITION OF FLUOROETHER COMPOUND FOR ANESTHETIC USE, METHOD FOR STABILIZING A FLUOROETHER COMPOUND, USE OF STABILIZER AGENT FOR PRECLUDING THE DEGRADATION OF A FLUOROETHER COMPOUND
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The present invention has as objective the stabilization of a fluoroether compound against degradation by acid substances. The stabilizers proposed are selected among appropriate pharmaceutical compounds and are used for preparing stable pharmaceutical compositions of a fluoroether compound. Method for stabilizing a fluoroether compound and use of stabilizers agents for precluding the degradation of a fluoroether are also described.
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Page/Page column figure 2
(2008/06/13)
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- Trimethylsilyl fluorosulfonyldifluoroacetate (TFDA): A new, highly efficient difluorocarbene reagent
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TFDA is readily prepared from the reaction of fluorosulfonyldifluoroacetic acid with trimethylsilyl chloride, and it is a very effective and efficient source of difluorocarbene for use in addition reactions to alkenes of a broad scope of reactivities. Acid-sensitive substrates may require an additional purification step involving treatment of the distilled TFDA with sufficient Et3N to remove the acid impurity. Other trialkylsilyl fluorosulfonyldifluoroacetates can also be prepared, and they have been found to have reactivities similar to TFDA. The triethyl derivative, TEFDA is more convenient to prepare in a pure state and has similar reactivity to TFDA. Thus, it may prove to be a superior reagent.
- Dolbier Jr., William R.,Tian, Feng,Duan, Jian-Xin,Li, An-Rong,Ait-Mohand, Samia,Bautista, Olivia,Buathong, Saiwan,Baker, J. Marshall,Crawford, Jen,Anselme, Pauline,Cai, Xiao Hong,Modzelewska, Aneta,Koroniak, Henryk,Battiste, Merle A.,Chen, Qing-Yun
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p. 459 - 469
(2007/10/03)
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- Chemiluminescent autoxidation of α-silyl carbanions derived from 9-silyl-10-methylacridanes
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The autoxidation of α-silyl carbanions derived from 9-trimethysilyl- and 9-triphenylsilyl-10-methylacridanes (1a and 1b) produced the fluorescent N-methylacridone (NMA) accompanied by weak chemiluminescence. Differences in the chemiluminescence quantum yields and the time course of the light emission were detected between the reactions of 1a and 1b, which was due to the substituent on the silicon atom. Additionally, the 9-trimethylsilyl-10-methylacridinium salt also underwent a chemiluminescent reaction when reacted with alkaline hydrogen peroxide. It is probable that these chemiluminescent reactions would proceed via the Peterson-type reaction and involve the dioxasiletanide-like species during the reaction pathway.
- Motoyoshiya, Jiro,Tokutake, Kunihiko,Kuroe, Motoki,Yoshioka, Sachiko,Nishii, Yoshinori,Aoyama, Hiromu
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p. 1667 - 1672
(2007/10/03)
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- Cleavage of arylalkylsilanes by sodium amide in liquid ammonia
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The aryl carbon-silicon bonds in arylalkyl monosilanes have been cleaved by sodium amide in liquid ammonia. Sub-stoichiometric amounts of amide effect complete cleavage of the aryl anion. Reactions were complete in just a few minutes at room temperature except when bulky alkyl groups are present (eg. triisopropylphenylsilane). In dialkyldiarylsilanes both aryl functions were rapidly cleaved with little selectivity when the aryl groups had different substituents. The influence of metallic cations was important (NaNH2, KNH2 >> LiNH2 > Ca(NH2)2). Solvent and temperature were also studied.
- Sun, Guang-Ri,He, Jin-Bao,Zhu, Hua-Jie,Pittman Jr., Charles U.
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p. 619 - 622
(2007/10/03)
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- Thermolysis of alkoxyaluminum and siloxyaluminum acylates
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Thermolysis of alkoxyaluminum acylates (RO)nAl(OCORt)3-n (n = 1, 2; R = i-Pr, s-Bu, t-Bu, Rt = Ph, CH2I; R = PhCH2, Rt = Me, Et, Ph; R = Me3Si, Et3Si, Rt = Me) was studied. The main direction of thermolysis of derivatives of primary and secondary alcohols and of unsubstituted carboxylic acids is ester and alcohol formation. Trialkylsiloxyaluminum acylates termolyze to give in the first stage no other products than trialkylacyloxysilanes. Thermolysis of iodoacylates (RO)2AlOCOCH2I (R = Pr, s-Bu) involves oxidation of the alkoxy group to carbonyl compounds with simultaneous formation of a ketene and hydrogen iodide. tert-Butoxyaluminum acylates regardless of the structure of substituent in the acyloxy group undergo symmetrization to aluminum tert-butylate.
- Stepovik,Kazakina,Martynova
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p. 1371 - 1377
(2007/10/03)
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- Procedures for the preparation of silanols
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Two procedures are described for the preparation of silanols and silanediols from the corresponding chlorosilanes.The first procedure, a two-phase hydrolysis-extraction process, is- particularly convenient and suited to the preparation of a wide range of mono-silanols.Hydrolysis of dichlorosilanes by this procedure gives varied results depending on the structure of the dichlorosilane and specific reaction conditions.The second procedure, a modification of a published procedure, is especially beneficial for the preparation of silanols and silanediols prone to undergo self-condensation. Key words: Silicon; Hydrolysis; Self-condensation; Silanols
- Cella, James A.,Carpenter, John C.
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- Rhodium Complex-Catalyzed Desilylative Cyclocarbonylation of 1-Aryl-2-(trimethylsilyl)acetylenes: A New Route to 2,3-Dihydro-1H-inden-1-ones
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Under water gas shift reaction conditions, 1-aryl-2-(trimethylsilyl)acetylenes undergo Rh-catalyzed desilylative cyclocarbonylation to give 2,3-dihydro-1H-inden-1-ones and trimethylsilanol.A wide variety of functional groups, such as methoxy, chloro, acetyl, ethoxycarbonyl, cyano, and trifluoromethyl, are tolerated on the aromatic ring under the reaction conditions.The products were obtained in good to excellent yield whether the substituent on the aromatic ring was electron-donating or electron-withdrawing.The cyclizations of substrates bearing a meta substituent onthe aromatic ring regiospecifically gave 5-substituted-2,3-dihydro-1H-inden-1-ones except when the meta substituent was a methoxy group.The desilylative cyclocarbonylation is an alternative to the conventional preparation of 2,3-dihydro-1H-inden-1-ones, an intramolecular Friedel-Crafts acylation.A possible mechanism for the process is described.
- Takeuchi, Ryo,Yasue, Hiroyuki
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p. 5386 - 5392
(2007/10/02)
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- Le (chlorodiisopropyl)silyl fluorenyllithium: un equivalent synthetique du diisopropyl(fluorenylidene)silene
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The metalation of chlorodiisopropylfluorenylsilane 1 with n-butyllithium leads to the α-silylthio compound 3.Compound 3 has a surprising stability and does not afford the diisopropyl(fluorenylidene)silene but behaves as its synthetic equivalent; i.e. it is a useful reagent for "Wittig-Peterson" reactions with various carbonyl compounds leading readily to diisopropylsilanone and fluorenylidene derivatives.
- Couret, C.,Escudie, J.,Delpon-Lacaze, G.,Satge, J.
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p. 233 - 242
(2007/10/02)
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- Process for purification of hydrochloric acid
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A process for purification of hydrochloric acid containing hydrogen fluoride, which process comprises steps of: contacting the hydrochloric acid containing hydrogen fluoride with at least one silicon compound of the formula: wherein X is chlorine, hydroxyl or OSiR4 R5 R6, and R1, R2, R3, R4, R5 and R6 are the same or different and alkyl groups having 1 to 4 of carbon atoms, and recovering a trialkylfluorosilane compound produced in said contacting step of the formula: wherein R1, R2 and R3 are the same as defined above, said recovering step comprising sub-steps of: hydrolyzing the produced trialkylfluorosilane compound (2) after the recovery thereof to convert to a trialkylsilanol compound of the formula: wherein R1, R2 and R3 are the same as defined above, and condensing the trialkylsilanol compound (3) to produce a hexaalkyldisiloxane compound of the formula: wherein R1, R2, R3, R4, R5 and R6 are the same as defined above, silicon compound mixture containing the hexaalkyldisiloxane compound as a main component present after said contacting and recovering steps being recycled to the contacting step for reuse, on the recycling, at least a portion of the silicon compound mixture containing the hexaalkyldisiloxnane compound being chlorinated to produce the trialkylchlorosilane compound.
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- Mechanism of Thermal Eliminations. Part 30. Pyrolysis of 2-Trimethylsilylethanol and 1-Aryl Derivatives
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The Arrhenius parameters (Eact = 45.57 kcal mol-1, log A/s-1 = 12.865) and rate coefficient at 600 K (1.84 * 10-4 s-1) for the cis β-thermal elimination of trimethylsilanol from 2-trimethylsilylethanol are identical (within experimental error) with those reported in the literature for elimination of methyl trimethylsilyl ether from 1-methoxy-2-(trimethylsilyl)ethane.This indicates that the driving force for the reaction, formation of the Si-O bond, is such that alteration of the nucleophilicity of oxygen has little effect on the reaction rate.A series of 1-aryl-2-trimethylsilylethanols have been prepared and their rates of elimination determined.The activating effect of the 1-aryl substituent (5.2-fold) is much less than the corresponding effect in the pyrolysis of ethyl acetates (63-fold) and 2-trimethylsilylethyl acetates (87-fold).Breaking of the α-C-O bond is thus kinetically less important than in the other reactions, and this conclusion is confirmed by a correlation of the rate data with the Yukawa-Tsuno equation which gives ρ = -0.4, r = 0.3.Si-O bond formation in the reaction is thereby shown to be of over-riding kinetic importance.For the 4-methylphenyl- and 4-methoxyphenyl compounds a minor competing reaction was the elimination of water to give the corresponding 1-aryl-2-trimethylsilylethene, and this has a higher activation energy than for the elimination of trimethylsilanol.NMR spectra for the 1-aryl-2-trimethylsilylethanols show that interaction between the OH and SiMe3 groups inhibits free rotation about the C(1)-C(2) bond.Preparation of 1-aryl-2-trimethylsilylethanols gave 1,3-diaryl-4-trimethylsilylbutyl trimethylsilyl ethers as byproducts arising from elimination of water from two molecules of the alcohols in a process believed to be two-step.
- Taylor, Roger
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p. 1703 - 1706
(2007/10/02)
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- PYROTHIOCARBONATES V. SYNTHESIS AND SOME REACTIONS OF S-TRIMETHYLSILYL O-ALKYLDITHIOCARBONATES
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Non-reported S-trimethylsilyl-O-alkyldithiocarbonates (2) are prepared by reaction of O,O-dialkyltrithiodicarbonates with N-methyl-N-trimethylsilylaniline in 87-96percent yield.These air-sensitive liquids which are separated from accompanying phenyl methyl alkylcarbamothioates by fractional distillation.The reaction of 2 with acetyl chloride gives the unsymmetrical dithioanhydrides S-acetyl O-alkyldithiocarbonates in 93-97percent yield.With the less powerfull electrophilic reagent, iodomethane, S-trimethylsilyl O-ethyldithiocarbonate (2a) forms S-methyl O-ethyldithiocarbonate in 30percent yield.When a chloroform solution of 2a is stirred with water the unstable compound O-ethyldithiocarbonic acid is obtained. Key words: Masked O-alkyldithiocarbonic acids; O,O-dialkyltrithiodicarbonates; S-acetyl O-alkyl-dithiocarbonates.
- Palominos, Mario A.,Vega, Juan C.
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p. 319 - 324
(2007/10/02)
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- REACTION OF HEXAMETHYLDISILOXANE WITH 2-ETHOXY-1,3-DIOXOLANE
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The reaction of hexamethyldisiloxane with 2-ethoxy-1,3-dioxolane is described.It is shown that cleavage of the endo- and exocyclic carbon-oxygen bonds of the ortho ester occurs under mild condition (16 - 20 deg C) in the presence of acidic catalysts with
- Zhurkina, I. P.,Nedogrei, E. P.,Musavirov, R. S.,Kondrat'eva, I. A.,Rakhmankulov, D. L.
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p. 1338 - 1342
(2007/10/02)
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- Photoinduced Hydride Reduction of NAD+ Analogue with Permethylpolysilanes Acting as Electron Sources and Water as a Proton Source
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Photoinduced hydride reduction of an NAD+ analogue, 10-methylacridinium ion with permethylpolysilanes acting as electron sources and water as a proton source occurs efficiently in acetonitrile under irradiation of visible light (λ>360 nm) to yield 9,10-dihydro-10-methylacridine selectively.
- Fukuzumi, Shunichi,Kitano, Toshiaki,Mochida, Kunio
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p. 2177 - 2180
(2007/10/02)
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- Process for preparing polyisocyanato/polyisocyanurates by catalytic cyclotrimerization of polyisocyanates
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Polyisocyanurate/polyisocyanates of enhanced stability are prepared by partial catalytic cyclotrimerization of a polyisocyanate in the presence of a catalytically effective amount of an aminosilyl catalyst and wherein the cyclotrimerization reaction is terminated when a predetermined desired amount of isocyanurate groups has been attained, by adding to the reaction mixture, after the cooling thereof to a temperature of below 50° C., a reaction terminating amount of an organic catalyst deactivating compound comprising at least one free hydroxyl moiety, or the reaction product of such hydroxylated organic catalyst deactivating compound with an isocyanate.
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- PH DEPENDENCE OF HYDROLYTIC REMOVAL OF SILYL GROUP FROM TRIALKYLSILYL ETHERS
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Rate constants for the acid and base-catalyzed hydrolysis of the trialkylsilyl ethers of alcohols were quantitatively correlated with Taft's ?* and Es values of the substituens on Si and O atoms of the ether linkage.The regression equations for kH and kOH were satisfactorily computed.
- Shirai, Naohiro,Moriya, Kiyoshi,Kawazoe, Yutaka
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p. 2211 - 2214
(2007/10/02)
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- THE TAUTOMERISM OF HYDROXY DERIVATIVES OF FIVE-MEMBERED OXYGEN, NIRTOGEN, AND SULFUR HETEROCYCLES
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The unstable enolic tautomers 3-hydroxyfuran, 2- and 3-hydroxy-thiophene, 3-hydroxy-pyrrole, 3-hydroxy-1-methyl-pyrrole and their benzo-derivatives have been generated in solution and the rate and equilibrium constants for their ketoization determined.
- Capon, Brian,Kwok, Fu-Chiu,Road, Pokfulam
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p. 3275 - 3278
(2007/10/02)
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