Abstract The Rochow Reaction is the copper-catalyzed, one-step synthesis of methylchlorosilanes f... more Abstract The Rochow Reaction is the copper-catalyzed, one-step synthesis of methylchlorosilanes from metallurgical grade silicon and methyl chloride. Cu3Si has been described as the catalytically active phase, but zinc and tin are required as promoters for high selectivity to dimethyldichlorosilane. We have studied the fundamental surface-chemical phenomena occurring in the reaction by XPS and XPS/MS. The paper will focus on the composition of the catalytically active surface, the surface enrichment of Zn, Sn, and Si and the mechanistic implications of the enrichment.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The acid ionization constants of estrone (i0.77), 178-estradiol (i0.71) and 2-methoxyestrone (10.... more The acid ionization constants of estrone (i0.77), 178-estradiol (i0.71) and 2-methoxyestrone (10.81) have been determined spectrophotometrically and shown to be consistent with the additivity of substituent effects on the phenol ring. Previously published values for estrone
60 OC. Chromatography on a 12 X 1 in. silica gel column have a crude yellow product which was pur... more 60 OC. Chromatography on a 12 X 1 in. silica gel column have a crude yellow product which was purified by preparative thin-layer chromatography. Benzene-hexane (1: 1) developed a yellow band which yielded 0.03 g of a semicrystalline yellow material, which was not successfully purified, and an orange band. The latter was rechromatographed with use of pure benzene to give 0.1 g (18%) of the desired product as orange crystals, mp 202-205 'C.
How would you describe to the layperson the most significant result of this study? Silicones are ... more How would you describe to the layperson the most significant result of this study? Silicones are synthetic materials composed of silicon, oxygen, and hydrocarbon groups that can be specifically tailored for av ast range of technological applications. As true all-rounders, silicone oils and rubbers are used in computers and electronics, textiles and personal care from head to toe, automobiles and architecture, greatly influencing everyday life. The starting materials used to create silicones are efficiently produced at huge scales worldwide, but in this process formation of an unwanted residue is unavoidable. Notwithstanding decades of research on recovering value from the residue stream, tens of thousands of tons of this waste are incinerated annually.T he results of this study demonstrate a surprisingly simple recovery procedure that turns the waste efficiently into the most valuable building blocks in high demand in the silicones industry.
Abstract A combination of chemical and spectroscopic investigations have proven that the corrosio... more Abstract A combination of chemical and spectroscopic investigations have proven that the corrosion layer on Copper-7 intrauterine devices (IUDs) consists primarily of copper(I) and copper(II) species with lesser amounts of calcium, iron, and nonmetallic components. Photoacoustic spectroscopy of the intact layer as well as wet chemical analysis combined with atomic absorption spectroscopy has allowed evaluation of both metal composition and copper oxidation state percentages, which vary appreciably from sample to sample. Results indicate that the copper oxidation is caused by oxygen and not by oxidized glutathione as suggested earlier by others.
Pt nanoparticles of sub-3 nm diameter immobilized within a crosslinked polysiloxane network coval... more Pt nanoparticles of sub-3 nm diameter immobilized within a crosslinked polysiloxane network covalently attached to a silica support have been shown to be highly efficient recyclable leach-resistant catalysts for olefin...
A unique microstructure‐driven self‐sorting of chemically indistinguishable side chains in alkyl ... more A unique microstructure‐driven self‐sorting of chemically indistinguishable side chains in alkyl siloxanes is reported for the first time. The difference in cooperativity among the side alkyl chains caused by the variation in backbone microstructure is the key to drive this self‐sorting. The study also reveals that while alkyl chains of random and fully blocked siloxane discriminate each other, the alkyl chains of partially blocked siloxane can form crystals with both polymers resulting in reinforcement of the mechanical property of the blends.
A positive correlation between calcium-carbonate coatings on copper-7 IUDs and contraceptive fail... more A positive correlation between calcium-carbonate coatings on copper-7 IUDs and contraceptive failure of the device is reported. 5 of 23 copper-7 IUDs removed from pregnant women had extensive calcium-carbonate deposits. 3 other copper-7 devices removed from women with suspected pregnancy also had extensive calcium-carbonate deposits. It is suggested that extensive coating of the device would appreciably slow the release-rate of copper thereby reducing its efficacy. It is suggested that any IUD which releases an active agent may have its efficacy limited by the accumulation of calcium salts. A slow acid release at the surface of an IUD may solve the problem of carbonate build-up.
L'invention concerne des complexes de cobalt contenant des ligands pyridine diimine tridentee... more L'invention concerne des complexes de cobalt contenant des ligands pyridine diimine tridentee et leur utilisation comme catalyseurs efficaces et selectifs de silylation deshydrogenante, d'hydrosilylation et de reticulation.
L'invention concerne un procede de production d'un produit silyle, comprenant la reaction... more L'invention concerne un procede de production d'un produit silyle, comprenant la reaction d'un melange comprenant (a) un compose insature contenant au moins un groupe fonctionnel insature, (b) un hydrure de silyle contenant au moins un groupe fonctionnel d'hydrure de silyle et (c) un catalyseur, eventuellement en presence d'un solvant, pour produire un produit silyle deshydrogenant et un produit hydrosilyle ou une combinaison d'un produit silyle deshydrogenant et un produit hydrosilyle, le catalyseur etant choisi parmi un complexe pyridinediimine-dicarboxylate de cobalt ou un compose de type carboxylate de cobalt et le procede est realise sans preactiver le catalyseur via un agent reducteur et/ou sans compose initiateur ou promoteur. On a trouve que les presents catalyseurs sont actifs en presence de l'hydrure de silyle utilise dans la reaction de silylation.
The reaction between cuprous chloride CuCl and silicon is the classical model reaction for activa... more The reaction between cuprous chloride CuCl and silicon is the classical model reaction for activation of the contact mass in Direct Synthesis. It had been found by several authors that the reactivity of CuCl strongly depends on its quality and the route of synthesis. In the present study the reactivities of two CuCl charges, prepared from the elements at high temperatures and by reduction in aqueous solution, are compared by means of calorimetric studies. The aqueous route CuCl was found to have a higher reactivity, indicated by lower reaction start temperatures and 100% CuCl conversion with respect to the other charge. It was found that the reactivity depends neither on intrinsic properties (defect concentration) nor on properties that can be derived from microscopical or thermoanalytical characterizations or by X-ray powder diffraction. The initial step of reaction between cuprous chloride and silicon was identified as a solid state reaction. Therefore, the role of the CuCl surface is discussed and a model for the initial step is suggested.
Abstract The Rochow Reaction is the copper-catalyzed, one-step synthesis of methylchlorosilanes f... more Abstract The Rochow Reaction is the copper-catalyzed, one-step synthesis of methylchlorosilanes from metallurgical grade silicon and methyl chloride. Cu3Si has been described as the catalytically active phase, but zinc and tin are required as promoters for high selectivity to dimethyldichlorosilane. We have studied the fundamental surface-chemical phenomena occurring in the reaction by XPS and XPS/MS. The paper will focus on the composition of the catalytically active surface, the surface enrichment of Zn, Sn, and Si and the mechanistic implications of the enrichment.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The acid ionization constants of estrone (i0.77), 178-estradiol (i0.71) and 2-methoxyestrone (10.... more The acid ionization constants of estrone (i0.77), 178-estradiol (i0.71) and 2-methoxyestrone (10.81) have been determined spectrophotometrically and shown to be consistent with the additivity of substituent effects on the phenol ring. Previously published values for estrone
60 OC. Chromatography on a 12 X 1 in. silica gel column have a crude yellow product which was pur... more 60 OC. Chromatography on a 12 X 1 in. silica gel column have a crude yellow product which was purified by preparative thin-layer chromatography. Benzene-hexane (1: 1) developed a yellow band which yielded 0.03 g of a semicrystalline yellow material, which was not successfully purified, and an orange band. The latter was rechromatographed with use of pure benzene to give 0.1 g (18%) of the desired product as orange crystals, mp 202-205 'C.
How would you describe to the layperson the most significant result of this study? Silicones are ... more How would you describe to the layperson the most significant result of this study? Silicones are synthetic materials composed of silicon, oxygen, and hydrocarbon groups that can be specifically tailored for av ast range of technological applications. As true all-rounders, silicone oils and rubbers are used in computers and electronics, textiles and personal care from head to toe, automobiles and architecture, greatly influencing everyday life. The starting materials used to create silicones are efficiently produced at huge scales worldwide, but in this process formation of an unwanted residue is unavoidable. Notwithstanding decades of research on recovering value from the residue stream, tens of thousands of tons of this waste are incinerated annually.T he results of this study demonstrate a surprisingly simple recovery procedure that turns the waste efficiently into the most valuable building blocks in high demand in the silicones industry.
Abstract A combination of chemical and spectroscopic investigations have proven that the corrosio... more Abstract A combination of chemical and spectroscopic investigations have proven that the corrosion layer on Copper-7 intrauterine devices (IUDs) consists primarily of copper(I) and copper(II) species with lesser amounts of calcium, iron, and nonmetallic components. Photoacoustic spectroscopy of the intact layer as well as wet chemical analysis combined with atomic absorption spectroscopy has allowed evaluation of both metal composition and copper oxidation state percentages, which vary appreciably from sample to sample. Results indicate that the copper oxidation is caused by oxygen and not by oxidized glutathione as suggested earlier by others.
Pt nanoparticles of sub-3 nm diameter immobilized within a crosslinked polysiloxane network coval... more Pt nanoparticles of sub-3 nm diameter immobilized within a crosslinked polysiloxane network covalently attached to a silica support have been shown to be highly efficient recyclable leach-resistant catalysts for olefin...
A unique microstructure‐driven self‐sorting of chemically indistinguishable side chains in alkyl ... more A unique microstructure‐driven self‐sorting of chemically indistinguishable side chains in alkyl siloxanes is reported for the first time. The difference in cooperativity among the side alkyl chains caused by the variation in backbone microstructure is the key to drive this self‐sorting. The study also reveals that while alkyl chains of random and fully blocked siloxane discriminate each other, the alkyl chains of partially blocked siloxane can form crystals with both polymers resulting in reinforcement of the mechanical property of the blends.
A positive correlation between calcium-carbonate coatings on copper-7 IUDs and contraceptive fail... more A positive correlation between calcium-carbonate coatings on copper-7 IUDs and contraceptive failure of the device is reported. 5 of 23 copper-7 IUDs removed from pregnant women had extensive calcium-carbonate deposits. 3 other copper-7 devices removed from women with suspected pregnancy also had extensive calcium-carbonate deposits. It is suggested that extensive coating of the device would appreciably slow the release-rate of copper thereby reducing its efficacy. It is suggested that any IUD which releases an active agent may have its efficacy limited by the accumulation of calcium salts. A slow acid release at the surface of an IUD may solve the problem of carbonate build-up.
L'invention concerne des complexes de cobalt contenant des ligands pyridine diimine tridentee... more L'invention concerne des complexes de cobalt contenant des ligands pyridine diimine tridentee et leur utilisation comme catalyseurs efficaces et selectifs de silylation deshydrogenante, d'hydrosilylation et de reticulation.
L'invention concerne un procede de production d'un produit silyle, comprenant la reaction... more L'invention concerne un procede de production d'un produit silyle, comprenant la reaction d'un melange comprenant (a) un compose insature contenant au moins un groupe fonctionnel insature, (b) un hydrure de silyle contenant au moins un groupe fonctionnel d'hydrure de silyle et (c) un catalyseur, eventuellement en presence d'un solvant, pour produire un produit silyle deshydrogenant et un produit hydrosilyle ou une combinaison d'un produit silyle deshydrogenant et un produit hydrosilyle, le catalyseur etant choisi parmi un complexe pyridinediimine-dicarboxylate de cobalt ou un compose de type carboxylate de cobalt et le procede est realise sans preactiver le catalyseur via un agent reducteur et/ou sans compose initiateur ou promoteur. On a trouve que les presents catalyseurs sont actifs en presence de l'hydrure de silyle utilise dans la reaction de silylation.
The reaction between cuprous chloride CuCl and silicon is the classical model reaction for activa... more The reaction between cuprous chloride CuCl and silicon is the classical model reaction for activation of the contact mass in Direct Synthesis. It had been found by several authors that the reactivity of CuCl strongly depends on its quality and the route of synthesis. In the present study the reactivities of two CuCl charges, prepared from the elements at high temperatures and by reduction in aqueous solution, are compared by means of calorimetric studies. The aqueous route CuCl was found to have a higher reactivity, indicated by lower reaction start temperatures and 100% CuCl conversion with respect to the other charge. It was found that the reactivity depends neither on intrinsic properties (defect concentration) nor on properties that can be derived from microscopical or thermoanalytical characterizations or by X-ray powder diffraction. The initial step of reaction between cuprous chloride and silicon was identified as a solid state reaction. Therefore, the role of the CuCl surface is discussed and a model for the initial step is suggested.
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