Trace amounts of tin

Corbin HB. 1970. Separation and determination of trace amounts of tin present as organotin residues on fruits. J Assoc Off Anal Chem 53 140-146. 

Tin has a long, colorful history. This metal was discovered first in Thailand over 2000 years ago. Early craftsmen discovered that bronze - a noncorrosive metal that is extremely hard and strong enough to be used for spears, swords, arrows, and other especially important objects at that time - could be produced by smelting tin with copper. Tin is also the primary constituent of pewter. Long ago, people developed the belief that trace amounts of tin seemed to help prevent fatigue and depression, and that drinking out of tin cups could help combat these ailments. Tin... 

Tin can be separated from molybdenum by co-preeipitating tin(IV) with Fe(III) by adding ammonia to make the pH 6-8 [16]. Trace amounts of tin have been isolated by oxine with A1 as a carrier [17]. Tin can also be precipitated from acid medium (HCl, H2SO4) as the sulphide. Copper, Mo, or Cd may be used as scavengers [11]. 

It has been reported [107] that 1,4-butanediol (BD) and 1,4-butane diisocyanate (BDI) can be used as chain extender to modify commercial PLA in two steps. In first step, the commercial PLA melt is allowed to first react with BD in the presence of trace amount of tin (11) 2-ethylhexanoate to obtain hydroxyl terminated PLA (OH—PLA) [Fig. 5.20(a)]. And then, in the second step, BDI is added to react with hydroxyl end groups of OH— PLA to achieve chain-extended PLA, leading to the formation of urethane [Fig. 5.20(b)]. 

Natural fresh waters contain only trace amounts of tin (0.01-1 xg/l), with concentrations of about 3 xg/l in sea water. Aquatic organisms can accumulate tin (bioconcentration factor is 10 -10 ). Some microorganisms may methylate inorganic compounds and dealkylate synthetic organometallic compounds. Tin concentrations in soils are in the range of 2-200 mg/kg dry matter. 

Solutions in contact with polyvinyl chloride can become contaminated with trace amounts of lead, titanium, tin, zinc, iron, magnesium or cadmium from additives used in the manufacture and moulding of PVC. V-Phenyl-2-naphthylamine is a contaminant of solvents and biological materials that have been in contact with black rubber or neoprene (in which it is used as an antioxidant). Although it was only an artefact of the separation procedure it has been isolated as an apparent component of vitamin K preparations, extracts of plant lipids, algae, livers, butter, eye tissue and kidney tissue [Brown Chem Br 3 524 1967]. 

The [SaN]" cation was first obtained in low yield in 1978 by the oxidation of S7NH with SbCls. The reaction of in situ generated [SN]" salts with sulfur (Scheme 5.3) or the reduction of the [ClSNSCl] cation with anhydrous tin(II) chloride in SO2 or CH2CI2 can be used to prepare [S2N] salts. The best large scale synthesis involves the reaction of AsFs with a mixture of S4N4 and sulfur in the presence of a trace amount of bromine (as a catalyst) (Eq. 5.10). ... 

Tinplate and Solder. Metallurgical studies were performed to determine the effect of irradiation at low temperature on the corrosion resistance of tinplate and on the mechanical properties and microstructure of tinplate and side-seam solder of the tinplate container. The area of major interest was the effect of low-temperature irradiation on the possible conversion of the tin from the beta form to the alpha form. In the case of pure tin, the transition occurs at 18 °C. It was feared that low-temperature irradiation would create dislocations in the crystal lattice of tin and enhance the conversion of tin from the silvery form to a powdery form rendering the tin coating ineffective in protecting the base steel. Tin used for industrial consumption contains trace amounts of soluble impurities of lead and antimony to retard this conversion for several years. 

Aluminum is a soft, ductile, and relatively inexpensive metal. The surface of aluminum readily oxidizes in the air and water to form a highly resistant oxide film. This oxide film serves to make aluminum resistant to attack when used in environments containing sulfides, sulfur dioxide, carbon dioxide, and other corrosive gases. It is highly resistant to water-initiated corrosion, but is susceptible to galvanic corrosion by trace amounts of copper, tin, lead, nickel, or carbon steel. The reaction of aluminum in water to form Bayerite is shown in FIGURE 9-2. 

Elements are incorporated into teeth from the diet or by inhalation. The figure shows trace element profiles measured by laser ablation—plasma ionization-mass spectrometry of the dentine of teeth from a modem person and one who lived in Scandinavia about a.d. 1800. The contrast is striking. The old tooth contains significant amounts of tin and bismuth, which are nearly absent in the modern tooth. The old tooth contains more lead and antimony than the modem tooth. Tin and lead are constituents of pewter, which was used for cooking vessels and utensils. Bismuth and antimony also might come from pewter. 

To a solution of 41 (448 mg) (Eq. (17)] in toluene (10 mL) was added TBTH (3 mmol) and a trace amount of AIBN. The solution was then heated under argon for 2.5 h at 110°C. After evaporation of the solvent, the residual foam was dissolved in acetonitrile (30 mL), and the solution was extracted three times with hexanes to remove several tin compounds. The acetonitrile was evaporated, and the residue was purified by chromatography over silica gel (40 g) to yield 165 mg (83%) of 42. 

Reaction of the 1,2-thiazetidine 1,1 -dioxide 68 with the weaker Lewis acid, tin(iv) chloride, gives the CM-aziridine as a major product together with benzophenone (Equation 2). However, when the reaction is carried out on the /raor-isomer, it affords essentially benzophenone accompanied by a trace amount of the /ra r-aziridine <1998T8941>. 

The structures of both the phenyl and 2,5-dimethylphenyl tin clusters were established by single-crystal X-ray diffraction. Under similar conditions, toluene was stannylated to produce a mixture of organotin compounds. Bromination of this mixture yielded 3-bromotoluene and 4-bromotoluene in a 2 1 ratio, with trace amounts of 2-bromotoluene. Similarly, PhBr was produced upon treatment of the phenyltin product with aqueous Br2. No applications of the stannylation reactions have yet been reported. 

Trace amounts of catalysts, e.g., tin catalysts, are conveniently added by means of a pipette. The weight of one drop of catalyst can be determined in advance. Small amounts of catalyst can also be added by using an anal)rtical balance. However, the use of such a balance is not recommended because of disadvantages, including time-consuming weighing procedures and risks of over charge. 

In principle, if no further complications arise, the organotin residues should remain on the support and can be removed by filtration, so that the organic product can be recovered uncontamined by tin residues. Unfortunately, this expectation is too optimistic. When examined at trace level, variable amounts of tin... 

Trace amounts of noble and semi-noble metals (e.g., Au, Ag, Hg, and Cu) are separated electrolytically from acid media on a small platinum or gold cathode [81]. In cementation methods (i.e., reduction to metal in situ by another metal) small amounts of semi-noble metals (Cu, Bi, Sb) are deposited on less noble metals such as tin, iron, or zinc. 

Routledge et al. [7] investigated the formation of dihydrobenzofuran 1 from an aryl halide precursor (Scheme 1). With polystyrene, more than 1 equivalent of AIBN was required, while the reaction was complete within 20 h using 6 mol% of AIBN on TentaGel resin (which has a polyethylene spacer between the polystyrene and the site of compound attachment). Addition of t-butanol helped prevent an alternative y -elimination pathway. An attempt to force the latter was made with thiyl linker 2, but only trace amounts of the )9-elimination product 3 were formed. Also investigated were the cyclizations of iodides 4, in which the cyclization of an alkyl radical to an acetylene is approximately 10 times slower than the aryl radical cyclization to a double bond. A direct comparison of the same reaction on solution phase was attempted, but yields could not be determined for the latter because of contamination by tin residues. This illustrates one advantage of solid-phase radical reactions mediated by tributyltin hydride, namely the ease of product purification. 

The approach using trace amount of oxygen during tin anchoring will be denoted as route 3. 

Scheme 2 Tin anchoring in the presence of trace amount of oxygen...

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