Use Of Tin Research Articles

Modelling river channel topography using GIS

The modelling of environmental processes based on catchment elevation surfaces is well-established, but the use of TIN and grid surface models as three-dimensional representations of river channel topography at the reach scale is much less common. In this paper, surface modelling facilities in ARC/INFO GIS have been used to model the geometry of seven short sections of gravel-bed river channels in upland Britain from field surveys taken in 1976 and 1994. The methods used in converting field survey data and implementing bed-topography models as TIN and grid data structures are described. The use of derived surface models to define pool-riffle bedforms, estimate sediment budgets and assess channel change between surfaces of different dates are discussed and evaluated.

A Novel Activation Process for Autocatalytic Electroless Deposition on Silicon Substrates

An improved activation process using a system for the activator solution is reported. The process is applicable for autocatalytic electroless deposition of metals on rough as well as smooth/polished, n‐ and p‐type silicon substrates of all doping levels. Using the improved activation process, adhesion of more than for palladium deposits and for nickel deposits has been obtained. The etch rate of in the activator solution is low enough for it to be compatible with planar integrated‐circuit technology. The activator avoids the use of tin, which is undesirable in device fabrication.

Determination of Ultra-Trace Amounts of Total Mercury by Gold Amalgamation-Cold Vapor AAS in Geothermal Water Samples by Using Ozone as Pretreatment Agent.

Mercury in geothermal water samples, pretreated with ozone, was subjected to reduction-vaporization by use of tin(II) chloride. The mercury vapor was concentrated with a porous gold collector. Afterward, mercury vapor which had evolved from the heated collector was determined by cold vapor atomic absorption spectrometry (CVAAS). By using ozone as pretreatment agent, the time for the decomposition could be shortened and the blank value of mercury from reagents used was reduced. The permissible amounts of sulfide and thiosulfate ions, the main interference ions in reduction-vaporization of mercury, were 25 and 100mg dm-3, respectively. It means that the present method provides an improvement in the permissible amounts of these ions by several hundred times in comparison with the methods using no ozone. Ozone was also found to be effective as the pretreatment agent for organic mercury. The present approach was proved to be satisfactory as the pretreatment of the quantitative analysis of ultra-trace amounts of total mercury in geothermal water samples.

Solid-Phase Reactions of Diffusion Barriers of Ti and TiN to Copper Layers on SiO2

Thin films of Ti and TiN interposed between the Cu layer and SiO2 are examined as a diffusion barrier as well as an adhesion-promoting layer for Cu metallization technology. Solid-phase reactions and/or interdiffusion taking place in the Cu/Ti/ SiO2/Si and Cu/TiN/ SiO2/Si systems are examined by X-ray diffraction and the depth profiling method using Auger electron spectroscopy and X-ray photoelectron spectroscopy. The reduction of SiO2 through the formation of Ti-oxides occurs at the Ti/ SiO2 interface even in the as-deposited Cu/Ti/ SiO2/Si system. In addition to this, the formation of Ti5Si3 and interdiffusion which result in the formation of Cu–Ti intermetallic compounds due to annealing at 450° C are evident, and lead to intermixing of the whole system. The use of TiN instead of Ti drastically suppresses the reaction and interdiffusion, and the Cu/TiN/ SiO2/Si system is stable even after annealing at 850° C, though the incorporation of a small amount of Ti into the Cu layer is observed.

5-fluorouracil derivatives. 1. Acyclonucleosides through a tin (IV) chloride-mediated regiospecific ring opening of alkoxy-1,4-diheteroepanes

The reaction of 5-fluorouracil with the seven-membered acetals 1a-g in the presence of tin (IV) chloride, trimethylchlorosilane and hexamethyldisilazane at room temperature gives 1-{[3-(2-hydroxyethylhetero)-1-alkoxy]alkyl}-5-fluorouracils 2a-f and 1-{[2-(3-hydroxypropoxy)-1- isopropoxy]ethyl}-5-fluorouracil 2g in 31–86% yields. The presence of an heteroatom on the 1-position of the cycloacetal and the use of tin (IV) chloride, capable of a 1,4-chelation, seem to impose their influence in the regiospecific ring opening of 1a-g. The conformational analyses carried out on 2b and (1 R,3 R)-2e and (1 R,3 S)-2e clearly indicate that the N 1(sp 2)-C 1-C 2-C 3 moiety tends to fold in a gauche conformation. The antitumour activities of compounds 2b-g were assessed against HEp human cells showing that 2c is 4-fold more active than 5-FU. The drugs studied do not show any clear toxicity in comparison with the toxic effect of 5-FU.

A kit formulation of [ 131I] meta-iodobenzylguanidine (MIBG) using Cu(I) generated “ in situ” by sodium disulphite

A kit formulation of meta-iodobenzylguanidine (MIBG) ready to be labelled with 131I without purification step is presented. Radioiodination involves a nucleophilic exchange assisted by Cu(I) generated “ in situ” by sodium disulphite. The described labelling method allows high radiochemical yield and overcomes the problems associated with the use of tin as reductant. Chemical and radiochemical purity of [ 131I]MIBG and side products were determined by HPLC. The developed kit followed by a simple radiochemical manipulation allows to prepare [ 131I]MIBG at medical centres.

Stereoselective synthesis of both diastereomers of the .alpha.-methyl-.beta.-hydroxy-.beta.-alkyl(aryl) units by use of tin(II) triflate-mediated aldol reaction

Both diastereomers of the α-methyl-β-hydroxy-β-alkyl(aryl) units are prepared by the tin(II) triflate-mediated aldol reaction of 1-(ethylthio)-1-(trimethylsiloxy)propene with α-keto esters in high selectivities

Lubricated sliding wear of physically vapour deposited titanium nitride

Coated components are used in conjuction with uncoated materials in many tribological environments that contain lubricants developed for the uncoated substrates. There is no reason to believe that a lubricant optimized for a steel substrate will have a similar effect on the coated surface and thus there is a need to assess the effects of lubricants on the sliding wear of coated components and identify any deleterious lubricant-coating interactions. The lubricated sliding wear performance of titanium nitride films sliding against 52 100 steel and polycrystalline sapphire counterfaces was investigated as a function of coating microstructure for a range of different physical vapour deposition (PVD) processes. Improvements in both coating wear rate and lifetime have been found, even using unformulated base oils, though variations in behaviour between lubricants have been observed which can be determental. When the microstructure of titanium nitride coatings on steel substrates is open (zone 1), the use of an unformulated oil can improve wear performance until it is comparable with that of a fully dense film with the zone T microstructure. Furthermore, the use of lubricants led to a substantial improvement in wear lifetime over similar unlubricated coating contacts owing to reductions in the amount of coating detachment during wear. The presence of the lubricant reduces the amount of transferred material from the sliding counterface (particularly for the steel sphere), minimizing coating-counterface adhesion and hence friction which reduces the incidence of premature failure by coating detachment. The implications of these observations are discussed for the use of TiN coated components in real tribological applications.

ChemInform Abstract: A Highly Stereoselective Synthesis of α‐Glucosides from 1‐O‐ Acetyl Glucose by Use of Tin(IV) Chloride‐Silver Perchlorate Catalyst System.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Asymmetric aldol reaction between achiral silyl enol ethers and achiral aldehydes by use of a chiral promoter system

In the presence of a chiral promoter consisting of tin(II) triflate, a chiral diamine, and tributylin fluoride, the silyl enol ether of S-ethyl ethanethioate or S-tert-butyl ethanetioate reacts with aldehydes to afford the corresponding aldol-type adducts in good yields with high enantioselectivities. In the reaction of silyl enol ether of S-ethyl propanethioate with aldehydes, perfect stereochemical control is attained by the combined use of tin(II) triflate, a chiral diamine, and dibutylin diacetate. A wide variety of aldehydes, including aliphatic, α,β-unsaturated, and aromatic aldehydes, are applicable to this reaction. The chiral promoters are characterized by 119 Sn NMR spectra and proved to form the three-component complexes, which behave as chiral Lewis acids. The reaction proceeds directly from silyl enol ethers without any accompanying metal exchange on the enolates

A Highly Stereoselective Synthesis of α-Glucosides from 1-O-Acetyl Glucose by Use of Tin(IV) Chloride–Silver Perchlorate Catalyst System

Abstract In the presence of a catalytic amount of tin(IV) species generated from tin(IV) chloride and silver perchlorate, 1-O-acetyl-d-glucose stereoselectively reacts with silyl alkoxides to give the corresponding α-glucosides in high yields.

Endo selective cyclizations of selenonium ion intermediate: efficient formation of 1-halo-3-seleno-cyclohexanes

Selenoacetal 1 was cyclized with tin(IV) chloride in the 6-Endo-Trig mode to give 1-chloro-3-methylselenocyclohexanes ( 2a,b), regio- and stereoselectively. Bromo- or iodocyclohexane derivatives were afforded by use of tin(IV) bromide or titanium(IV) iodide, respectively.

A New Efficient Chiral Catalyst System. Combined Use of Tin(II) Oxide, Trimethylsilyl Triflate and Chiral Diamine in the Asymmetric Aldol Reaction

Abstract The asymmetric aldol reaction between both achiral silyl enol ethers of thioesters and aldehydes is efficiently catalyzed by the use of a new catalyst system consisted of tin(II) oxide, trimethylsilyl triflate and a chiral diamine, to give the corresponding adducts in high yields with high diastereo- and enantioselectivities.

Synthesis and Crystallography of Sodium Titanium Bronze

An alternative reaction for the preparation of sodium titanium bronze (STB) based on the use of TiN as a reductant has been tested. Crystallographic data for STB available from the literature and from new preparations have been compiled and discussed.

Determination of iodine in seaweed and table salt by an indirect atomic-absorption method

Decomposition methods based on fusion with alkali are discussed, with respect to the determination of iodine in biological material. It is shown that sodium hydroxide can be used for the decomposition of seaweed without loss of iodine. In spite of the oxidizing conditions, the iodine will be present as iodide in the final ash. The iodide can be determined by an indirect atomic-absorption method, based on the reaction between iodide and mercury(II), with determination of mercury by cold vapour atomic-absorption spectrometry. The basis of the method is discussed, and it is shown that the use of tin(II) as reductant is essential. The effect of the oxidation state of the iodine on the sensitivity of the method is pointed out. High concentrations of chloride interfere, but it is still possible to determine iodide in iodinated table salt.

Catalytic use of tin(II) reagents in organic synthesis

New carbon-carbon bond forming reactions using a catalytic amount of tin(II) reagents have been developed. Namely, an aldol type reaction of tin(II) enolate is achieved starting from α,β-unsaturated ketone, aldehyde and ethylthiotrimethylsilane in the presence of a catalytic amount of tin(II) triflate sulfide. Furthermore, the catalytic asymmetric Michael reaction of tin(II) enethiolate is realized just by using a catalytic amount of tin(II) triflate-chiral diamine complex.

ChemInform Abstract: New Possibilities in the Michael Reaction by the Use of Tin(II) Enolates.

Abstract3‐Propionyl‐2‐oxazolidone (I) is converted to the tin(II) enolate and then treated with cyclohexenone (II) in the presence of acidic catalysts to produce the isomeric adducts (III) and (IV).

New Possibilities in the Michael Reaction by the Use of Tin(II) Enolates

Abstract The Michael addition reaction of tin(II) enolates with α,β-unsaturated ketones proceeds smoothly by the use of chlorotrimethylsilane as an activator to give the corresponding addition products in good yields.

Tin(II) chloride in the analytical chemistry of the platinum metals: From the “purple of cassius” to polyurethane foams

Tin(II) chloride has played a central role in the non-instrumental analytical chemistry of the platinum group metals, the characteristic reaction between tin(II) chloride and platinum(II/IV) chloride having been documented for more than 180 years. The intense colour of hydrochloric acid solutions containing small amounts of Pt(II/IV) and tin(II) chloride constituted one of the first trace colorimetric methods for the determination of Pt in the sub parts per million range. Similar spectrophotometric methods of trace analysis for Rh have been known for more than half a century. Remarkably the detailed nature of the interaction of tin(II) chloride with the platinum group metals has only been elucidated relatively recently, and there is evidence of recent renewed interest in platinum group metal complexes involving the SnCl 3 − moiety as ligand. We wish here to give a brief history of the use of tin(II) chloride in the analytical chemistry of the platinum group metals, highlighted by some of our recent work involving the selective immobilization of chloro(trichlorostannato)platinum/rhodium complex anions by polyurethane foams as a means of separation and pre-concentration of small amounts of Rh and Pt.

Electrophoresis of thiols in cellulose cells : I. General Approach

Cellulose gels have been produced by decomposition of viscose with ethylenediamine and potassium hydroxide in glass tubes. The rods obtained have been used for solving thiols in acidic neutral media in a xylene bath. The thiols are extracted from aqueous solution as tributyltin mercaptides followed by stripping with hydrochloric acid in glycerol, adn a 0.2-ml sample is placed at the top of the gel which is in a vertical position. A preliminary separation of thiols into five groups based on the extraction properties is recommended. A method for reducing disulphides based on the use of tin(II) as the reducing agent and extraction of thiols as tributyltin mercaptides is suggested. The application of the complex of tetramercurated fluorescein with uric acid for the detection and fluorimetric determination of thiols is described.